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herman pahls
10-26-2015, 12:44 AM
Some of my grandkids are outgrowing the roll cage of their mini buggy which is powered by a 6.5 HP Predator engine and a GTC self contained torque convertor.
I am considering a new build using the Harbour Freight Predator 13 hp engine.
I have been very pleased with the 6.5 Predator and GTC self contained TC.
I have been waiting for GTC to come out with a self contained TC for the 13 hp engine. Go Karts USA says that GTC is developing a self contained TC but it has not been ready to market yet.

1. Does the Harbour Freight Predator 13 hp engine have a good reputation like the 6.5 does.
2. Are there other engines to consider in this power range?
3. Is it worth waiting for the GTC self contained TC or would I be better off buying the pieces and making my own jack shaft assembly for the driven part of the torque convertor?
4. It appears the Predator 13 hp is electric start. Does the engine come with a charging system to maintain the battery.
Thanks
Herman

tazmannusa
10-26-2015, 07:55 AM
The 13 hp is not bad for the money and it does have a charging system, not as smooth running as the Honda GX 390. I put one in a spider kart for a friend and other than braking chain master links every once in a while they are real happy with it. I have one in my little buggy with stage 1 kit but with governor still intact and so far it is still running good , key switch block has broken off a couple times from the vibration and that is the only problem with the engine so far. Personally I would not run a self contained TC on the bigger engines, the driven jack shaft is only supported on one end. on mine I'm running double jack shafts with 3 bearings each and had to switch to 530 chain from the pivot to axle.

dain254
10-26-2015, 12:30 PM
I am running one in my little buggy - just rode it this weekend, still rips! They are unbeatable for the money in my opinion.

herman pahls
10-26-2015, 01:29 PM
Thanks for the response both tazmannusa and dain254.
530 chain for 13hp, that is what I run on my hayabusa powered car.
Do you mind sharing some info regarding your machines.
Weight, size (length and width, performance (top speed and performance)and photos of your drive train and suspension.
Herman

herman pahls
10-26-2015, 01:40 PM
Taz
I also was concerned about the self contained TC and only being supported on one end.
On the 6.5 hp self contained TC, I made a support for the driven end.
So what TC's are you suggesting for the 13hp?
Are you using 530 chain from the 1st jack shaft to the 2nd and 530 from the 2nd to the axle?
I assume you used 2 jack shafts to get the required gearing with the 530 chain size.
What ratios did you end up with and rear tire diameter?
thanks
Herman

dain254
10-26-2015, 02:28 PM
You can see my build on here - http://www.minibuggy.net/forum/show-off-your-toys-here/21480-single-seat-mini-baja-type-buggy.html

I go into some detail about the rear end - I use 530 chain as well, only because it is indestructable for the most part, especially with 13hp. weight is about 400lbs, its just a lil guy - but it's pretty much the most fun thing I've ever driven.

65chedderbob
10-26-2015, 06:15 PM
My build has an old 447 ski doo snowmobile engine in it and I run 530 chain from the jackshaft to the axle, mainly because that's what size sprockets the buggy came with, but also because it is strong. Looking back though I probably should have thrown a support bearing in the middle of the shaft, because while I was cleaning up the splines on the end that goes into the chaincase on the lathe I found that the shaft was a little bent :o

tazmannusa
10-26-2015, 07:08 PM
Taz
I also was concerned about the self contained TC and only being supported on one end.
On the 6.5 hp self contained TC, I made a support for the driven end.
So what TC's are you suggesting for the 13hp?
Are you using 530 chain from the 1st jack shaft to the 2nd and 530 from the 2nd to the axle?
I assume you used 2 jack shafts to get the required gearing with the 530 chain size.
What ratios did you end up with and rear tire diameter?
thanks
Herman

The 40 series will work ok with a buggy on the lighter side , I went with the 780 series because it has a low low and good overdrive ratio plus the wide belt . If I remember correctly I ended up with about a 6.7:1 ratio with 20 x 10 knobby tires. The wifes is the size of the edge sidewinder with the stock Honda GX390, 40 series TC , 6:1 ratio , and 22" knobby tires. Works out ok with the #40 chain but if we play on hills much the belt is short lived, The jack shaft on that one is just forward of the engine with a 12 tooth to a 72 tooth on axle.
Mine is a different animal, engine is 6" above swing arms and needed the second shaft inline with pivot I had the #40 chain on both but with better than 2:1 on top of 3:1 was a bit much on the 3:1, kept stretching and snapping master links so I swapped the 3:1 to #50 sprockets and 530 chain, I got a few good hours of running it last weekend and the 530 is holing up good

tazmannusa
10-31-2015, 12:16 PM
Ran across this, uses steel pate rather than aluminum, might be good if you need a really compact unit
40 Series TAV (http://www.gopowersports.com/40-series-torque-converter-kit-bolt-on/)

herman pahls
11-01-2015, 01:40 PM
Taz
Thanks for the info on the 40 Series TAV option.
I did not realize that was available.
Since you have experience with 13HP engines, TC's, chain sizes and ratios, I would like to learn from your experience.
Would your wife's buggy be easier on belts if the gearing was say 8:1 ?
Would the top speed be adequate at 8:1 ?
To get 8:1 with #40 chain in one step would require a 10 and 80 tooth sprocket.
The 80 is 13" in diameter and the 10 would be quite small for chain and sprocket wear.
Dual jackshafts would allow more ideal sprocket diameters but would add complexity in fabrication and chain adjustment.
#50/530 sprockets become even larger in diameter to get the desired reduction.
Tell me more about the 780 series CVT's?
I would appreciate your thoughts before I move forward with this build.
Thanks
Herman

tazmannusa
11-01-2015, 06:00 PM
Herman
The belts on my wifes I think we just got a cheap belt last time around so I just ordered Kevlar comet belts, cost about double. going with a little lower gearing or 20" tires would help on belt life , just depends on what top speed your looking for, this one tops out about 40, kind of a happy medium. I found that running a 10 tooth on the front I would get a lot more vibrations and howling at certain higher RPM's with the #40 chain. on the spider kart that I did we went with a 10 and 60 tooth, 20" tires but the throttle was limited to about half so it worked out good.
Big difference between the 780 and the 40 series, the 40 has a 1:1 high and 2.43:1 low where the 780 has .69:1 high and 3.71:1 low. I double checked and mine is running 6.8:1 ratio so I get 25.228:1 low and 4.69:1 high, Wifes gets 14.58:1 low and 6:1 high. Not sure about the HP rating on the 780 some places advertise it at 16 HP and others I have seen as high as 22. Size wise the 780 is a lot bigger so you need a little more room for it. I haven't had to do any fine tuning with weights or springs it just worked out of the box , just gearing started with 6:1 but it bogged a bit in high. They do make a few different driven's for the 780 a 770,780,790 just depends on if you want higher or lower gearing
Tom

herman pahls
11-02-2015, 10:21 PM
Taz
Thanks for taking the time to post details like the ratios.
It seems clear to me the advantage of using the 780 series is the wide gearing available from 3.71 to .69 overdrive vs the 2.43 of the 40 series.
This allows for less reduction needed in the sprockets, therefore a smaller diameter sprocket on the axle where ground clearance is an issue.
So is Comet really out of business to get the Duster or 780 series?
Seems like the Baja SAE guys are sourcing this stuff and I assume it is not used.
Thanks again
Herman

tazmannusa
11-03-2015, 06:53 AM
From what I understand comet went out of business but another outfit bought or took it over. The 780 is still available from quite a few places , I bought mine from
Search (http://beltpalace.com/nsearch.html?section=&query=780&searchsubmit=Search+ITEM+or+BELT+NUMBER%3A&vwcatalog=yhst-42732163996146)
If you have room run a little longer belt and CD , I went with the 9.05" CD #300625 belt but when the belt is cold it is stiff and causes a little drag, after it warms up a minute or two it's fine
Tom

herman pahls
01-07-2016, 01:03 AM
I am committed to a build.(For kids 6-10 years old, will not fit adults)
I purchased the Polaris Predator front suspension and coilovers.
Also the wheels and tires, Kids suspension seat, rear axle, bearings and wheel flanges.
I ordered a 13HP Predator today.
Dain254 build was the motivating factor so it is all his fault.

Now for the CVT decision.

I am considering Comet 780 series like Taz used which gives the widest shifting ratio (approx. 3.71 to .69) I have seen for around $530. (driver,driven and belt).
The driven is also 9.05" in diameter which creates a "keep the driven out of the dirt" issue on Dain's rear suspension design which I want to copy.
The Comet 40 series sells for about $300 at BMIkarts.com .
BMI has a no name 40 series CVT system for around $150.
I believe Dain is using the no name BMI CVT with success.
The 40 series drivens are 7.5" in diameter.

I would appreciate any feedback on the quality/longevity of the BMI no name 40 series CVT parts before I make a decision.
Thanks
Herman

Bullnerd
01-07-2016, 05:05 AM
"Dain254 build was the motivating factor so it is all his fault." LOL!

ProtoDie
01-07-2016, 07:12 AM
Herman,
we tried 40 series clutches years ago on 6.5 motors in the MXT kids cars
they worked,,,ok,,, but over 3600 rpms they would shred belts in no time.
they would not last an hour at 5000 rpms
could be the belts we were using,,,,I do not remember,,, what ever belt they sent with the package we bought

We use CV-tech clutches and they work great.
a lot of SAE baja teams use these too

I listed specs on these in another thread

CV-Tech Clutches (http://www.minibuggy.net/forum/protodie-buggy-group/21802-cv-tech-clutches.html#post312720)

tazmannusa
01-07-2016, 08:50 AM
Protodie
I thought it was the 30 series you had belt problems with ?
I'm still debating on what system to use on my dual 6.5's , really be pushing the 30 series and the 40 series driver is 1" bore , did find a 44 magnum driver in 3/4" bore with 18 hp 8500 rpm rating.

Herman
I have bought and used a few of the china 40 series, on one driven I had to file the bore to fit the shaft and one driver after about 15 to 20 hours use gets sticky and I have to take it apart clean and lube and then it's fine again. other than than that they work and I think the last set I bought on ebay for about $100.
For a kids only buggy I think the 40 series would be good enough, your'e probably going to want to limit there top speed anyway

ProtoDie
01-07-2016, 09:42 AM
Protodie
I thought it was the 30 series you had belt problems with ?
I'm still debating on what system to use on my dual 6.5's , really be pushing the 30 series and the 40 series driver is 1" bore , did find a 44 magnum driver in 3/4" bore with 18 hp 8500 rpm rating.

Herman
I have bought and used a few of the china 40 series, on one driven I had to file the bore to fit the shaft and one driver after about 15 to 20 hours use gets sticky and I have to take it apart clean and lube and then it's fine again. other than than that they work and I think the last set I bought on ebay for about $100.
For a kids only buggy I think the 40 series would be good enough, your'e probably going to want to limit there top speed anyway




Taz
I had to go look at the obsolete parts shelf,,,,,,brr its cold over on that side
but I found a bunch of stuff I forgot I had lol

you are right though, it was 30 series not 40 we were blowing up
30 series is 3/4 wide belt and 40 series 7/8 wide belt

my bad [smilie=smackbottom:

so I can't really say on the 40 series clutches

dain254
01-07-2016, 09:55 AM
I have a CVtech sitting around - but my 40 series comet knockoff has been working great with the predator (40 drive and 44D driven - 44D is 1" bigger on the OD giving a higher CVT reduction. I'm guessing the cheap 40 driven that is 7.5" would work just fine though). I will likely make use of the CVtech when I build my 22hp version

herman pahls
01-07-2016, 12:51 PM
Bullnerd
This is America, somebody else is to be blamed for my actions.
I got bit by a clean, fairly simple build by a former SAE Baja member that also incorporates the front suspension and plastic off of Quads.
I like the way he utilized the rear steer from the Quad upright without messing with the geometry trying to switch to front steer.

Jody
Thanks for listing the Specs. on the CVtech CVT's.
When I read your SS630R build I was surprised by your low geared 13:1 box to get 45 MPH.
The .45 overdrive of the CVtech explains the math.
The CVtech prices are right in line with the Comet 780 series.
Does CVtech offer a combination with 1:1 or very little overdrive?
I am trying to copy Dain's rear suspension with 20" tires and 5:1 reduction on the sprockets to keep the rear sprocket as far away from the sand as possible and top out at ~40mph at 3600 rpm.

Dain
Thanks for letting me know that you are using the bigger diameter 44D Driven for lower gearing.
Do you have any clue what the high end ratio of your combination is? 1:1 ?
Thanks everyone for you responses.
Herman

dain254
01-07-2016, 01:13 PM
No idea - seems like BMIkarts had a link at one time for belt lengths and such. It accelerates well and tops out in the mid 30's, of course that information is useless without my gear ratio and tires! 1:1 is probably fairly close, I don't think I get much overdrive especially with the harder yellow springs installed.

ProtoDie
01-07-2016, 01:47 PM
Bullnerd
This is America, somebody else is to be blamed for my actions.
I got bit by a clean, fairly simple build by a former SAE Baja member that also incorporates the front suspension and plastic off of Quads.
I like the way he utilized the rear steer from the Quad upright without messing with the geometry trying to switch to front steer.

Jody
Thanks for listing the Specs. on the CVtech CVT's.
When I read your SS630R build I was surprised by your low geared 13:1 box to get 45 MPH.
The .45 overdrive of the CVtech explains the math.
The CVtech prices are right in line with the Comet 780 series.
Does CVtech offer a combination with 1:1 or very little overdrive?
I am trying to copy Dain's rear suspension with 20" tires and 5:1 reduction on the sprockets to keep the rear sprocket as far away from the sand as possible and top out at ~40mph at 3600 rpm.

Dain
Thanks for letting me know that you are using the bigger diameter 44D Driven for lower gearing.
Do you have any clue what the high end ratio of your combination is? 1:1 ?
Thanks everyone for you responses.
Herman


the specs I listed are what they have in this engine hp size, so I do not think they have 1:1

I think the overdrive is an advantage

when we tested in our MXT karts with 13hp a few years back, I was testing and working directly with CV-tech engineers to tune in the clutches for our application

we were at 6:1 with 20" tires
They told us we need more gear reduction for the clutches to fully travel and optimum performance.
They were right and at 6:1 the clutches did not maximize travel so we were not achieving maximum performance and did not get the top speed or the full potential of the engine and clutches

I am currently putting the 670 predator and 20" tires in a couple of MXT buggies for a customer
his kids compete in sand drags here in Michigan
8.5:1 is the gear ratio I am going with to start for 20" tires
To get this ratio and more ground clearance ( no huge rear sprocket)
I am designing up a new swing arm engine plate and clutch mount set up with 2 jack shafts
this gives me a huge range of ratios with smaller,,, cheaper sprockets

Of course I wish I could get the ratio I want with one chain,,,,but I can't,, and want to optimize power and performance of these engines and clutches

design work is almost done on this and we will be ordering laser tomorrow.
building them up in a week or two
I will up date the MXT section with this setup when we get building them

dain254
01-07-2016, 03:00 PM
Part of squeezing performance out of lower HP engines is really cutting down on your rotating mass and losses everywhere - the CVtech drive/driven is huge compared to the 40 series - so not only is it trying to spin up the inertia of those big pulley but it has a big fat belt it has to bend around them too resulting in more drive loss. Now send the power through a gearbox, chains, bearings etc you've taken your 13hp and turned it into 6 by the time it reaches the ground :D

ProtoDie
01-07-2016, 05:09 PM
While I do agree with that to a point...

I have done different quite a few different size buggies engines and clutches.
Not maximizing your clutch potential with proper gear reduction has shown me the greatest loss of power and performance.

with my gear chart calculator the theoretical max speed of the SS630R buggy showed
the best to be 45.77 mph with 13:1 gear reduction
max 3600 rpms

714 lb buggy with 25" tires
200lb driver (depending on the day,,,,during the holidays,,,maybe 205 LOL)
so with driver and fuel,,probably 920 to 930lbs
running thru a 40lb gear box gears and oil and CV-tech clutches
independent rear suspension,,, so rotating mass of cvs and axles are more weight than a straight axle

hit 44.6 mph on GPS

I was expecting to be 80% of theoretical top speed (that would be 37 mph),,, so very pleased with that and the clutches were getting full potential of travel doing their job well

our MXT buggies are 350 to 400lbs with straight axle and did not hit that top speed with the 13hp engine running almost 5000 rpms, straight axle,,, less weight and less rotating mass

difference is the gear reduction was off in the MXT testing and not maximizing the clutches potential

RPM gear boxes agreed and also recommended 13:1 in the gear box they built me for the SS630R

most of the time they run 7:1 to 10:1 in their CVT gear boxes
the 3.9:1 to 5.4:1 gear boxes are only for shifter motors because they are not enough gear reduction for CVT

dain254
01-07-2016, 05:27 PM
In your 2 seater your top speed sounds like its limited by the governor if it is still intact, as is the top speed on my buggy. Your parastaltics wind resistance and all other losses would be the limiter if you were ungoverned or when your motor lets go!

You are also building ultra reliable machines where squeezing size out of parts will affect longevity and durability, so the CVtech/Rpm/CV is likely what Id have chosen too for that application!

ProtoDie
01-07-2016, 05:48 PM
Thanks Dain
the governor and motor is all stock on the 2 seat

The 13hp we tested with the CV tech clutches years ago had the governor pulled, and lots of other upgraded parts and would run 6000-7000 rpms with a mechanical clutch but only hit 5000 with the CVT
I wish I could go back and swap gear ratios on that one, but at the time we were maxed out at 10T to 60T with one chain

I'll have more data from the 2 jack shaft set up,,,,, depending on Michigan weather.
gonna suck if I have the 2 MXT buggies ready to test with 670 motors,,,,and 3 feet of snow......then its wait till spring,,
or clear the shop out and let my kids do burn out contests :D
if I do,,,, there will be video [smilie=giddy.gif]

tazmannusa
01-08-2016, 04:43 AM
One problem with my double jack shaft setup is the first chain gets hot if I run at top speed for any duration, #40 chain spinning on an 11 tooth at about 4800 rpm and that is with the Gov still intact. Been looking for a flat cog belt setup to replace the first chain but not able to find anything yet, if I cant find any what I might end up doing is downsizing the chain to #35 gold race chain with a 16t to 34t sprockets vs the 11t to 25t in the #40 should run a little cooler, don't know if it will hold up to the torque though.

ProtoDie
01-08-2016, 07:27 AM
going to start with 2 sets of 14-40 420 chain
the smaller the sprocket the higher the heat

I agree, # 35 will probably run cooler
ran #35 on our 6.5 MXT karts with mechanical clutches running 7000 rpms
held up fine, but think I need at least 420 with this 670 engine 20" tires and dual jack shaft set up

tazmannusa
01-08-2016, 08:30 AM
The 420 might hold up on the second chain, I ended up with the better 530 O ring chain with 12t to 36t sprockets 20" tires also. When I first swapped to the 530 I put on a cheap run of the mill 530 bike chain , not sure what happened but after my 13 year old gran daughter drove it a while the chain was stretched with a bent link so a trip to the bike shop and $100 fixed that problem. Mine only has the 420 engine with 780 clutches so your'e going to get a lot more torque hitting that second chain with the 670

herman pahls
01-08-2016, 09:02 AM
Dain
According to the tech department of certified parts (the owners of Comet), the CVT combination you chose gives 2.83 low and 1.24 high with the 8.5" dia 44D driven if my calculations are correct.
In my opinion those are perfect ratios for this build with 20" rear tires and 5-1 sprockets which gives approx. 35 MPH at 3600 RPM.

I want to use the 17 HP Comet reversing box since I need a jack shaft for the Driven regardless.
Have you thought about how to install the Comet box in your build so the driven will be in the same location?
My concern is whether the gear box is wide enough to get the out put sprocket far enough to the right for the chain to clear the engine on the right side or is that an issue?

Herman

dain254
01-08-2016, 11:54 AM
I haven't found a model of it yet to drop in mine, but it may end up needing to be coupled to get it all the way across... the chain needs to be far enough outside to clear the engine mount plate and the pull starter cover on the engine when the suspension compresses. I'm planning on using one for the next one I build, so we will see how it turns out!

herman pahls
01-08-2016, 05:36 PM
Good idea on coupling, simple solution I had not come up with.
The input and output shafts are concentric with each other.
The coupler would need a support bearing, but so does the Driven shaft side as noted in the instructions for installing.
It is 11.75" from driven shaft to output shaft.

herman pahls
01-08-2016, 05:44 PM
accidentally posted twice

dain254
01-09-2016, 10:25 AM
if the coupler was a tight pilot on the output shaft and to the extended piece OR welded to it the gearbox could simply hang between the two bearings under the engine with minimal bracing to keep it from rotating. Does anyone have a CAD model for it and I can work that into the design. Id not ill just order one.

ProtoDie
01-09-2016, 10:45 AM
no cad, but here is a link to some dimensions

http://www.bmikarts.com/PDF/CometGearBox.pdf

Bullnerd
01-09-2016, 11:23 AM
There is one of these for sale in South Jersey.

Comet go cart gearbox (http://southjersey.craigslist.org/for/5383846798.html)

dain254
01-09-2016, 01:07 PM
I took the dims from BMI and made a crude model that is surprisingly representative - The way a person would have to mount it is cut the CVT shaft short and make a coupler that would be held by the bearing on that side. The gearbox will completely replace the other jackshaft bearing and the gearbox output will be in the perfect spot to clear the motor case in a bottoming out scenario. No problem!

http://i1083.photobucket.com/albums/j395/dain254/CometReverseMount_zpsast6guk6.jpg

herman pahls
01-09-2016, 09:00 PM
Jody
Thanks for the gearbox dimensions.

Dain
I am impressed with your quick and simpler solutions regarding avoiding support bearings on both sides.
Would it simplify the gearbox installation if it was turned upside down from what you illustrated and bolted to the same plate the engine is?
The plate would have to be wider than for the engine alone with gearbox shifted to the right for the chain the clear the engine at full suspension compression.
Also the gearbox case would be protruding approx. an inch further forward than a 8-1/2" dia. driven which may get in the way of the seat and keeping the wheel base short.

Bullnerd
01-09-2016, 09:16 PM
Awesome job with model dain.

dain254
01-09-2016, 09:39 PM
With the gearbox being supported on the primary shaft, the mounting really doesnt need to be heavy at all. A couple flanges coming off the supporting bracket will be plenty, and could be tied into the case bolts! I didn't want to mount the box upside down since I assumed the gear oil would leak out the shift shaft. I'm still working on getting the model 100% before I build, coming along slowly.

herman pahls
01-10-2016, 10:06 PM
Dain

Good point regarding potential leaking at the shift shaft seal.
I also appreciate your modeling skills as Bullnerd commented.

Do the Polaris Predator Podium front shocks perform and hold up the front of your car well?
Was it Polaris RZR 800 rear coilovers you were trying on the rear?
Any comments on how they perform.
Seems like the back end on a RZR 800 would weigh several hundred pounds more than yours or you may be leveraging the shock more by increasing the motion ratio to get them to work.
I need to source some rear shocks for the build is my reason for asking.
Would you consider Fox Air (actually nitrogen filled) shocks for the rear? Like 4-6" travel.
I realize they cost $225 each and you may be finding used Polaris shocks for $100/pair on Ebay.
I have tried Fox Air Shocks on full size 2 seat sand cars and ended up replacing them with coilovers.
Seems like these shocks have a lot of what I call stiction (if that is how it is spelled?) where the shock sags and stays there in the situation where a 2 seater only has one person in it.
Maybe Fox air shocks work better on single seaters that are balanced.

Any Idea how much your 13hp buggy weighs.

Jody

Are you selling the Coilovers that you used on your Vegas builds?
What travel do they come in and can the springs be changed to accommodate 3-400 pound buggies?
I checked a few weeks ago and did not find them on your web site.

Thanks
Herman

dain254
01-11-2016, 07:51 AM
The podiums work great on the front of mine, and were just a little too soft for the rear - with the rzr 800 I am leveraging a bit more than the rzr would and I have a few different mounting points I am adding in to dial it. The rzr shocks are shorter than podiums so I switched back to a chinese pair I bought off ebay a while back which are too long and too stiff and am running those on my current machine.. they aren't great but work better than the podiums in the rear!

We used fox air shocks on one of our mini bajas, i've had them on snowmobiles... They are awesome if you are a person who doesn't mind messing with your shocks a bit here and there since they are finicky towards the correct setup.. and have nitrogen, I prefer a shock I bolt on and forget about!

ProtoDie
01-11-2016, 09:39 AM
Dain

Good point regarding potential leaking at the shift shaft seal.
I also appreciate your modeling skills as Bullnerd commented.

Do the Polaris Predator Podium front shocks perform and hold up the front of your car well?
Was it Polaris RZR 800 rear coilovers you were trying on the rear?
Any comments on how they perform.
Seems like the back end on a RZR 800 would weigh several hundred pounds more than yours or you may be leveraging the shock more by increasing the motion ratio to get them to work.
I need to source some rear shocks for the build is my reason for asking.
Would you consider Fox Air (actually nitrogen filled) shocks for the rear? Like 4-6" travel.
I realize they cost $225 each and you may be finding used Polaris shocks for $100/pair on Ebay.
I have tried Fox Air Shocks on full size 2 seat sand cars and ended up replacing them with coilovers.
Seems like these shocks have a lot of what I call stiction (if that is how it is spelled?) where the shock sags and stays there in the situation where a 2 seater only has one person in it.
Maybe Fox air shocks work better on single seaters that are balanced.

Any Idea how much your 13hp buggy weighs.

Jody

Are you selling the Coilovers that you used on your Vegas builds?
What travel do they come in and can the springs be changed to accommodate 3-400 pound buggies?
I checked a few weeks ago and did not find them on your web site.

Thanks
Herman


yes, just need to get them up on the site yet

These are Empi shocks.
The stock coil springs are not good, but we made a conversion kit to put good coil springs on these,,,,made all the difference in the world.
Real happy with how they perform after the spring change
16.5" eye to eye extended
10.5 compressed, so 6" travel

After conversion to good springs these are $110 each
should be available on our site in the next couple of days.
I am running 1 7/8" dia springs 180lb front and 220lb rears on 714lb buggy
springs rates available from 100lbs to 500lbs

herman pahls
01-13-2016, 12:07 AM
Dain
Any idea what the rear of your buggy weighs?
I want to order rear shocks form Jody at Protodie and need to have an idea what spring rates to order.

The 13 HP Predator arrived today and I need to order the same Torque Convertor pieces you did from BMI.
Do you mind sharing the center to center distance on your set up and what of belt you suggest?
BMI is selling 11 - 11/16th's inch C-C belts for $10.00 due to overstocking.
I am concerned about quality at that price.


It appears that you raised the stock 13hp gas tank several inches above the engine instead of leaving it attached to the engine.
Do you mind sharing why?

Any plans for sale yet?

Thanks
Herman

dain254
01-13-2016, 09:30 AM
Herman,

Plans are not close to being done - I am busy with my day job as an engineer and don't always feel like engineering when I get home. The next iteration of the buggy will allow the tank on the 13hp to remain mounted to the engine. There was not enough space in the original which is why it is mounted above.

C-C distance on my current is shorter than it will be on the new which is somewhere between 11-13", that cheap belt may work, but I don't know yet! I'm sorry I haven't created plans yet but there is a lot of information I need to compile and vehicle testing needs to be completed before I will put my name on something I'm selling!

herman pahls
01-13-2016, 10:38 AM
Dain
Thanks for C-C and tank mounting info.
I actually like the appearance of the engine with the tank remotely mounted but that requires added fabrication.
I understand your dilemma, If I was a fabricator for my day job I would struggle doing the same for a hobby.
I appreciate you sharing info to get me started.
Time to order more parts.

dain254
01-13-2016, 12:35 PM
I definitely prefer the tank just be mounted to the engine - it just worked out that way while fitting the 22hp engine, the 13hp in the same mounting slots works out to keep it attached! If you are a good fabricator and can design a little bit I would think you could take all of the information about my buggy from the forum here and replicate it with a little effort without plans.

herman pahls
01-13-2016, 02:57 PM
Dain
Are you using 530 chain on the 13 hp buggy?
Seems like you said you were using 10T and 50T sprockets.
BMI has the 50T, 530 sprockets but the smallest front sprocket in 530 is 13T for a buggy they sell parts for.
I am curious where you sourced a 10T 530 sprocket if that is what you are using?
Thanks
Herman

dain254
01-14-2016, 01:53 PM
hmmm.. i dont remember - might have been surpluscenter.com.

tazmannusa
01-15-2016, 07:51 AM
Yep surpluscenter has a 10 tooth #50
For an under slung gear box this one might be an option for low HP
Go Kart Forward / Reverse Kit | Go Kart Parts | Racing Karts | Engines | Frames | Tires | Tips | Kits | Torque (http://www.bmikarts.com/Go-Kart-Forward-Reverse-Kit_p_3680.html)
From what I understand about it the input shaft is setup for the 30 series TC and has reduction of 1.3:1. One guy on the kart forum bought one and liked it, he had a new input shaft made to fit the 40 series and longer to accept a outer support bearing but he has not reported back yet as to how well it works. As cheap as they are I might get one and install it in a chassis I built about a year ago

herman pahls
01-17-2016, 12:15 AM
Hello Taz
Thanks for confirming that Surplus Center has #50 size 10 tooth sprockets as Dain suggested.
The reversing box you referred to from BMI is a bargin but I am concerned about it holding up to 13 HP.
If I go with the reversing box I will go with the Comet from BMI for $245 since it is rated for 17HP.
Using the reversing box both simplifies and complicates the build in my opinion.
It will take the place of the Jack shaft for the driven and allow for another set of sprockets to get the needed reduction with out using extreme small and large (in the dirt) diameter sprockets.
Reverse is a big plus.

The negative is drag, weight and the fabrication of figuring out a way to easily adjust another chain. I try to avoid idler sprockets to take the slack out of the chain.
Should I be avoiding idler sprockets?

Should I stay with the more convenient to use (and less money) industrial 50 sized sprockets and chain or go with the narrower and lighter motorcycle 520 chain that most likely is not available in 10,11 or 12 tooth sprockets that fits a 3/4" keyed shaft?

How do these keyed sprockets and shafts hold up with extended use?
I have always used splined sprockets in the past for dirt bikes.

Xbird
01-17-2016, 06:31 AM
go with 1" keyed, no worries at the level you're working with. skip the idler sprocket because alignment pretty much has to be spot on. Go with a 2x chain width spring loaded roller wheel or guide as a tensioner instead. It's a lot easier to to set the chain/s up, lock it all in place and take the slack up with a tensioner than it is to continually futz with keeping everything tight and in place as the chain stretches in. the subaru engine mount link i used as a tensioner in my LTz conversion works beautifully.

tazmannusa
01-17-2016, 08:38 AM
Herman
I couldn't resist the price on the gear box so I ordered one , if it looks good I may get a second one and use them on my twin 6.5's setup in a small two seater.
I avoid idler sprockets, engine on slotted plate and driven jack shaft on slots. the second jack shaft fixed at pivot point and the swing arm uses 3/4 x 5/8 rod ends.
For low HP the keyed sprockets hold up fine, only problem is the set screws come loose so you have to check them regularly, best bet there is run split aluminum lock collars to keep sprocket and key in place. You get more chain vibration and noise when running over a small sprocket, the bigger the chain the worse it gets with higher RPM's . The smoothest with the least amount of maintenance is the setup on my wife's 12t to 72t #40 chain but the 72t is huge, I did a friends 10t to 60t same 13 HP and 40 series , better ground clearance but more vibration and noise and he does brake master links every so often. Last year my neighbor bought what looked like a spider box kart, it had the 10 HP Subaru 40 series clutches, double jack shafts running #35 chains and they seemed to hold up fine, very little vibration or chain noise even though the chains were rusty, smallest sprocket looked to be about 16 tooth. I guess what I am trying to say IMHO is don't go with 10t if it's a higher RPM application and you want it to last

herman pahls
01-17-2016, 11:11 PM
Hi Xbird
You suggested going with 1" keyed which is what I am using for the axle.
The Driven is on a 3/4" shaft and has a 3" long key and the drive sprocket (1" wide) on this shaft only has a 1" key.
My concern is will that 1" key start working the keyways and get sloppy.
I wish those sprockets came with a split so they can be clamped to the 3/4" shaft to prevent the keyways from getting sloppy in the first place
Any ideas or am I over thinking the road I have not been down before?

Taz
I also lean towards slotting the engine and jackshaft plates to allow adjustment.
Does the jackshaft to engine distance need to be adjustable once you set the Comet recommended Center to Center distance for the Driver, Driven and Belt?
If that distance is fixed and does not need adjustment, I am considering bolting the engine and jackshaft (or Comet reversing gearbox) to a plate and making that plate slotted to move engine/jackshaft to adjust the first chain.
It sounds like your 2nd jackshaft is concentric with your rod end pivot so the 2nd chain maintains constant adjustment.
Do you have any photos that you do not mind sharing that show how you are using your 3/4 x 5/8th's rod ends and what kind of rear suspension you have?
Are those rod ends adjusting the chain from the 2nd jackshaft to the rear axle?
Thanks sharing your experience with sprocket sizes, chain noise and vibration.
By using a 2nd jackshaft (double reduction) there is no need to use less than 12 tooth sprockets with # 40 chain and the bigger sprocket should not be in the dirt.
Seems like you where using 530 chain on the second reduction?
Thanks for the info and responses.
Herman

Xbird
01-18-2016, 07:08 AM
for keyed sprockets, i went back to my old school bowling alley mechanic days and started putting nail polish on the keys, set screws and shafts. that ended all the loosening issues i was continually chasing then and there. if the set screws don't loosen up, you won't have any problems with the keys/keyways. For disassembly, heat or pour acetone over the works to dissolve the nail polish.

dain254
01-18-2016, 09:08 AM
Herman - if you measure everything perfectly and are using the rear swingarm setup I'm using, you technically don't have to slot anything! The rod ends on the swingarm are what give you the chain adjustment. I have the engine slotted in the design though since I'm not sure what length of belt I will use yet, and likely there will be some variance on where the two pulleys end up simply because each person's build might turn out slightly different... so slotting insures everything will still line up even it it is a little off!

tazmannusa
01-18-2016, 05:41 PM
Herman
Yep pictures are better than trying to explain
The first two pictures of the green one is mine, swing arm is experimental, articulation is adjusted by the size and type of material of the two connecting bars between swing arms. I wont say it is the cats meow yet but it does give a heck of a lot better ride than a ridged swing arm. The third picture is the wife's with the 12 and 72 tooth sprockets, chain adjustment is done with the driven jack shaft.
I have notice that on the 30 and 40 series CVT, setting the CD to spec for the belt length just works and on the 780 series you have to run it a little less till the belt gets worn in a bit
Tom
http://i190.photobucket.com/albums/z127/tazmannusa/002_3.jpg (http://s190.photobucket.com/user/tazmannusa/media/002_3.jpg.html)
http://i190.photobucket.com/albums/z127/tazmannusa/003_1.jpg (http://s190.photobucket.com/user/tazmannusa/media/003_1.jpg.html)
http://i190.photobucket.com/albums/z127/tazmannusa/001_3.jpg (http://s190.photobucket.com/user/tazmannusa/media/001_3.jpg.html)

dain254
01-19-2016, 08:30 AM
Taz - I like your setups (very similar to mine). I also like the idea to build in "flex" into the first kart, the first swingarm I built was similarly sized, bent it big time landing off of a jump! I had kicked around an idea of building in articulation by confining the chain drive to one side of the swingarm (bearings and a tiny jackshaft) and then connecting across with a couple small U-joints. Doing so would allow the chain drive to articulate with the rear axle without any articulation between the sprockets! I keep mine rigid so my kart lifts it's inside rear tire in a corner giving me lots of grin inducing oversteer.

herman pahls
01-19-2016, 12:28 PM
Xbird
Fingernail polish; I like the idea of poor mans Loctite, maybe better than Loctite in this application.

Dain And Taz
I appreciate the photos and commentary.

Flyrider on this forum says on his posts "overcomplicating mini buggies since 2005".

What attracted me to Dains build was the simplicity and Taz's build is very similar for rear suspension.
I find myself wanting to overcomplicate this build because I feel a need for independent rear suspension.
Independent rear suspension should probably have a differential and a sway bar plus I already committed to a reversing box.

I like Taz's sway bar concept (connecting bars) for limited articulation and preventing the trailing arms from turning into a parallelogram.
I was considering buying from Trophykarts.com their billet trailing arms that are connected together with what they call an "X Brace".
The X prevents the parallelogram and the large center bolt between the front part of the X and the rear part allows for limited articulation (Trophy kart uses a sway bar with this set up).

Dain
Regarding your idea of short jack shaft and U joints.
Both Trophy kart and Protodie do not seem to have issues with the chain twisting.
It would be interesting to know how much twist over what distance a chain can tolerate.

Taz
If you lift up a rear tire, how much articulation do you get?
What a great idea you came up with.
Will hardware store quality all thread in the 5/8th's or 3/4" diameter work?
Thanks
herman

tazmannusa
01-19-2016, 04:06 PM
Don't use all thread, the front one is just temp, to start with I had 3/4" .120" wall
Had a nice ride that way but broke where the inside nuts are. The rear one is solid flex proof material "I cant remember the grade" it holds up good. The 3/4" all thread is to stiff and if I really bind it hard will work the nuts loose. Plan is to get some sway bar material from wrecking yard to experiment with. One other thing the bushings that the bars go through if I used keyed and had key way in bars then it would not work the nuts loose from the twisting. I haven't measured the actual articulation, to me it more the ability to absorb a bump or pot hole on one side with out getting whiplash and not to much body roll. At the moment I can stand on one side and pull over on the top cage and it will twist over a few inches, jerk it a bit and it will go more . I don't drive it that hard jumping and such, well maybe a little bit, so I try to keep it on the softer side

herman pahls
01-20-2016, 12:14 PM
Taz
Sounds like you need an engineering metallurgy degree to figure out your connecting bars/ sway bars.

tazmannusa
01-20-2016, 02:11 PM
Taz
Sounds like you need an engineering metallurgy degree to figure out your connecting bars/ sway bars.

LOL It would help
Actually when I first came up with the idea I was talking to an old friend of mine about it, He said just build it the way you think it will work, if it don't work change it. I think even if I could run the numbers on it it would still be trial and error

tazmannusa
01-21-2016, 09:29 AM
Herman if you haven't come up with a rear swing arm setup you like yet, take a look at the ShredderII builds, if your kart is wide enough it looks to me to be a simple reliable setup and I like the way the disk brake rotor is mounted on the jack shaft, gives a lot better braking power with less unsprung weight

herman pahls
01-24-2016, 02:18 AM
Hi Taz
I have checked out several Shredder2 threads since you suggested the idea.
I am planning on building trailing arms similar to the Shredders except I considering running a chain down each arm (instead of CV axles) as I have seen a few builds on this forum.
That means an extra chain, but the concept seems like the easiest way to get 10-12" wheel travel and only be 50" wide on the rear tires.
I like the idea of the brake rotor being on the jack shaft for more braking power.
Now I need to inquire from the Shredder builders what tubing size and thickness they are are using on their trailing arms to not be twisting them.
Thanks for the ideas.
Herman

tazmannusa
01-24-2016, 07:56 AM
The twin chain setup like that should be pretty simple and reliable, dust, dirt, and mud is heck on chains so I would be looking at getting O ring chains.
Been working on my 2 seat 2 engine design, going for simple and reliable, all most thought about doing it without suspension till I took the trax II kart out for a spin in between the rains, kicked up to top speed about 35mph coming back home, hit a little pot hole and the ass end was 2' in the air front about 1' with a sideways twist , came down with the grace of a super ball. put the idea of no suspension out of the equation

herman pahls
01-24-2016, 03:56 PM
Taz
Have you posted any photos of your twin engine design or given any details of what engines, drives being used and what motivated you to consider 2 engines?
I am curious if two 6.5 HP Predators are lighter than one 13HP?
The 13 I just purchased is a beast in comparison to the 6.5.
Sounds like your no rear suspension antics deserves some sort Olympic scoring.
Where is Yettem, CA?

Lug-Nuts
01-24-2016, 07:02 PM
Actually the shredder plans use a jackshaft and chain to each wheel. I modified mine to use cv's, and it's been a hit with other build's.

tazmannusa
01-25-2016, 07:45 AM
Taz
Have you posted any photos of your twin engine design or given any details of what engines, drives being used and what motivated you to consider 2 engines?
I am curious if two 6.5 HP Predators are lighter than one 13HP?
The 13 I just purchased is a beast in comparison to the 6.5.
Sounds like your no rear suspension antics deserves some sort Olympic scoring.
Where is Yettem, CA?

I still design and fab old school , draw them up full scale, so it's not anything that can be posted till I actually start building.
The two 6.5's are a little lighter than the 13 but by the time it's said and done the two would be a little heavier. Did some drawings over the weekend using the 6.5 swing arm mounted with 30 series clutches, sprocket and brake have to be mounted as outboard as they can, ground clearance is an issue, If I keep the suspension travel down to around 6" it would work, track width around 55" OD . Not the best option there
Yettem is about 40 miles SE of Fresno.
Scoring I Would not have scored to high, I saved it, now my wife, years ago we had one the the first model odyssey's, after a few cans of courage she was power sliding in a dried pond, caught and rolled 3 times and with that tall single roll bar and 22" balloon tires did not make for a graceful rolling. I would have scored that one 9 or 10

dain254
01-25-2016, 10:14 AM
two engines... I guess you could accomplish your drive with that but what a headache! I highly suggest looking at the rear driveline setup on mine - placing the jackshaft at the pivot of the swingarm and using the swingarm heim bushings to deal with chain tension simplifies everything a great deal. The updated design I'm working on has 11" of travel in the rear which is limited by the rzr800 shocks, longer shocks I could likely achieve nearly 15".

tazmannusa
01-25-2016, 12:10 PM
two engines... I guess you could accomplish your drive with that but what a headache! I highly suggest looking at the rear driveline setup on mine - placing the jackshaft at the pivot of the swingarm and using the swingarm heim bushings to deal with chain tension simplifies everything a great deal. The updated design I'm working on has 11" of travel in the rear which is limited by the rzr800 shocks, longer shocks I could likely achieve nearly 15".

Yep I hear yah
I built two with no suspension and they beat you to death and one with ridged swing arm suspension , heck of an improvement but still a bit rough then the one with flexing swing arm and it's even better, next will be IRS and two seats. Thing is I bought a few engines on sale when we were doing the first ones and some 30 series clutches so I'm determined to use them. It's pretty much going to be a kids kart but big enough for adults so 35 to 40 mph is fast enough. Another option is mounting the engines inline centered with trailing arms but I may end up scraping the idea of twins, went to HF and was drooling over the 670 hmm electric start charging system with battery, lights

dain254
01-25-2016, 07:27 PM
HA yeah that 670cc looks like a beast, I'm planning on using one for my upcoming build! For your kids buggy, you can always just drive one of the back wheels, it will get along just fine! - I'm big on keeping things simple!

tazmannusa
01-29-2016, 05:15 PM
Well I did get that gear box in that I posted about. kind if a neat little setup.
But the one I got has a bad bind to it when spinning by hand with the driven pulley.
BMI was not offering to exchange it, said it was OK so today I took it apart and checked everything, found one of the internal sprockets had two teeth machined off a bit causing it to bind up

herman pahls
01-30-2016, 09:13 PM
I am disappointed to hear that about BMI.
I am expecting a large order from them any day including a Comet reversing box.

tazmannusa
01-31-2016, 07:09 AM
I am disappointed to hear that about BMI.
I am expecting a large order from them any day including a Comet reversing box.

Iv'e never had any problems with them in the past but didn't get anything that was defective that needed exchanged .
I'm about ready to start building my little 2 seater. Was having problems keeping it small simple and light, ended up using Edges X2 concept on the cage with the old school fiberglass bucket seats, raking the rear hoop 10%. Allowed me to keep it down to 8'-2" length 44" wide and 42" tall. One thing that popped in my mind about IRS in this small and light of buggy , If one 200 lbs adult gets in is it going to hang lop sided ?

herman pahls
01-31-2016, 10:10 PM
Taz
I agree that a 2 seater suspension will sag to one side when not evenly loaded.
But what IRS suspension that is sprung for the typical off road 40 percent sag at ride height does not?
I would not stray away from IRS for that reason.
A sway bar may help.
Several years ago I built a 2 seat tube frame competition style rock crawler and used Fox air shocks since that is what was being used then on the single seaters.
I immediately switched to coilovers because of the pronounced sag when not evenly loaded and the stiction issue that air shocks have where they seem to resist equalizing like a coil over does in my experience.
Coil overs solved the problem

tazmannusa
02-01-2016, 04:43 PM
Herman
I will more than likely set it up on the stiff side , the buggy I'm trying to keep on the light side 400 Lbs and it will have from one 80 Lbs kid to two 200 Lbs adults.

tazmannusa
02-03-2016, 09:04 AM
Herman
Looks like I may have a change of plans , Had some VW stuff kinda fall in my lap.
So I may just build a class 9 car . It would be a good trainer for the gran kids plus if any of them want to do a little desert racing latter on they will have the chassis for it

Looks like BMI came through on the gear box, Sent me a return Auth# and there going to swap it out

herman pahls
02-09-2016, 01:34 PM
Hi Dain
Are you using a Thin Line steering rack on your 13HP car?
If so, I assume it is the 14" model and you adjusted the width of the Predator A-arms where they attach to the chassis to get the best steering geometry?
Thanks
Herman

dain254
02-09-2016, 03:06 PM
Correct, 14" - I think there are a few different brands that make essentially the same unit.. or 1 original and a bunch that stole the design! Someone else could likely talk about proper steering geometry with much more proficiency than I, but the basic principles I followed were to keep the tie rods as parallel to the arms as possible and as equivalent in length as possible keeping the rack low to fit under the foot board.

herman pahls
02-09-2016, 04:32 PM
Thanks Dain for replying.
Non of the photos that I have seen showed your steering rack, so it is nice to know that you placed it under the floor.
My plan is to duplicate the A- arm mounting points that Polaris had on the Quad except 10" wider to allow room for a foot box.
The big issue is like you said is to get the tie rod angles and length correct to minimize bump steer.
The steering geometry that the engineers at Polaris came up with is most likely worth copying.
Did you rake the A-arms up in the front like they are on the Quad?
I happen to own a Polaris Outlaw which is very similar to the Predator so I have something to refer to.
Is there a Quad that you prefer using the plastic from for the front and rear since you have been down this road already?
Herman

dain254
02-10-2016, 08:15 AM
I used the YFZ450 front and rear - the rear I cut up pretty significantly. It is certainly my recommendation to duplicate what was done from the factory on the A-arms. My original car is about 5 degrees of front kick up and the new one will have 10 - not sure how much is too little or too much, but more can't hurt!.

herman pahls
02-10-2016, 01:35 PM
Dain
Thanks for the YZF450 fender info.
Time for an E-bay search.
I assume you want the additional front kick up for better ride in the rough?
At some point, increasing the castor requires more steering force.
I have no clue where that point is.
My full size sand car has 10 degrees castor and steers easy without power steering.

herman pahls
02-18-2016, 05:21 PM
Finding a location for the Comet reversing box is turning out to be more difficult than I envisioned.
I am driving my rear wheels from a shaft in front of the 13 HP engine similar to what Dain did in his build except I am using 2 chains and independent rear trailing arms.
My wishes are to get the engine as low and as far forward as possible since this car is only 50" wide and approx. 61" wheelbase.
If I place the gearbox under the engine, the raises the engine at least 5 inches.
Also the gearbox input shaft needs to be about 5" above the bottom of the buggy to keep the 8.5" diameter driven out of the dirt which raises the engine even further.
If I place the engine behind the gearbox that moves the engine ~6" further back.
or I could move the seat 6" forward from where I want it to keep the engine forward.
If I move the gearbox behind the engine I would need to extend the gearbox input shaft, for the gear box to move to the right so the output sprocket will clear the right side of the engine.
This gearbox location also requires raising the engine some to keep the drive belt away from the exhaust on the left since that is where the Driven ends up.

So who's idea was it that these kids buggies need reverse?

Possibly I am over concerned about keeping the engine low and forward???

If there are any builds out there that show how they incorporated the Comet reversing box I would appreciate seeing how it was installed.

Thanks Herman

tazmannusa
02-19-2016, 07:17 AM
Herman
On my last one I raised the engine 6" for swing arm clearance and there is no noticeable difference compared to the ones the engine is at bottom frame level.
It is 52" OD wide and 68" wheelbase

dain254
02-19-2016, 11:08 AM
I cant advise on the two chains - I'm sure there are people that have plenty of success with them but I can't imagine the gain of IRS outweighs the deficit of having two chains to maintain and keep from flying off. I wouldn't think reverse is going to make the karts less fun!

herman pahls
02-20-2016, 11:42 PM
Dain
Like I confessed a while back I am already complicating this build in comparison to yours with 2 chains for IRS and 3 if I use the reversing box.
It appears your 13 HP engine is about 5-6 inches higher than the bottom of the chassis and it seems you do not have a top heavy issue?
My concern with incorporating IRS is that it will not lift the inside tire like yours does to allow steering by oversteer.
I am afraid the buggy will have a tendency to push unless I use a differential and possibly a sway bar.
Since you are an engineer, do you have any comments regarding whether a differential will allow this buggy to steer well with IRS rear suspension?

Taz
Great to get a 1st hand report that raising the 13HP engine 6" had no detrimental effect on handling.
That 13HP engine is amazing heavy compared to the 6.5 Predator
My concern with low center of gravity is that my 50# grand kid will be driving this thing and he has already rolled the 6.5 HP buggy.
Herman

dain254
02-22-2016, 01:16 PM
May seem ridiculous.. but you could always just drive 1 wheel in the back! The go-kart I had when I was 10 only had 1 wheel drive and it worked great! CVT to reverse box and chain off that to the single driving rear, DONE! :D

ProtoDie
02-22-2016, 03:31 PM
May seem ridiculous.. but you could always just drive 1 wheel in the back! The go-kart I had when I was 10 only had 1 wheel drive and it worked great! CVT to reverse box and chain off that to the single driving rear, DONE! :D


one wheel drive may work on a small go kart on pavement with good traction , but will send you in circles on dirt

herman pahls
03-01-2016, 05:47 PM
Dain
Since the primary use will be sand I need 2 wheel drive.
The issue with all builds is packaging the components so when you are done you are happy with the results and all performs well.

Regarding the Polaris Predator front suspension.

When measuring the Predator quad chassis that the donor front suspension came from, I noticed that the vertical spacing between the upper and lower A-arms where the A-arms attach to the chassis is about 1 inch more in front than the back.
I am curious if you duplicated that spacing in your build.
I happen to own a Polaris Outlaw quad with similar front suspension as the Predator and the Front A-arms are only 1/4" more vertically spaced in the front than the rear.
I assume the non parallel A-arms has a function like maybe Anti squat when braking.
I do not plan on using front brakes.

Since you are an engineer, do you mind sharing your thoughts on non parallel front A-arms and did you copy the concept when you used the Predator front suspension?
Thanks
Herman

herman pahls
03-31-2016, 10:23 PM
Aftermarket 13 HP (420cc) Predator air filter adaptors and exhaust.

My build it getting to the stage that I am installed the 13 HP Predator engine and Comet reversing box.
BMI karts supplied me with an air filter adaptor and choke plate for the 6.5 HP predator engine but they do not supply these parts for the 13 HP.
Affordable go karts supplies air filter adaptors for the Honda GX 340 and 390.
Is the Predator 420 a clone of these engines?
Thanks
Herman

makenzie71
03-31-2016, 11:56 PM
THe 420 is almost a straight copy of the GX390 and most of the parts swap right over. REading around on it seems there is a certain amount of risk with some parts, but the external parts seem interchangeable.

tazmannusa
04-01-2016, 12:11 AM
I bought the stage 1 kit from http://www.nrracing.com/product-p/stage1kit270-390.htm . If you get the header it's a long one and sticks out back behind buggy, I ended up cutting the flange off and making my own with the muffler. the jet that came with mine was way to small so I just drilled the original

herman pahls
04-03-2016, 05:45 AM
Makenzie
Thanks for the info on external parts interchanging between the Honda GX390 and clone engines.

Tazman
Thanks for sharing the nrracing.com site.

I wasted time Googling for this info you guys already knew it.
Herman

herman pahls
04-03-2016, 06:17 AM
I have wasted many hours trying to figure out how to package the Comet reversing box and the 13 HP Predator engine.
I am also complicating the build buy incorporating a differential.
If I place the reversing box in front of the engine I need to move the seat forward or move the engine back which just does not look right, plus it would move the weight too far back.
I considered installing the reversing box vertically which shortens the package 3" and requires re locating the vent on the box and still does not look right.
I looked into mounting the box behind the engine which gets the driven too close to the exhaust and would require extending the input shaft that the driven goes on.
Again, my opinion tells me that this option also does not look right.
I decided to place the engine above the reversing box because it allows the engine to move forward close to the back of the seat.
This requires the engine to be 6-7 inches higher which concerns me due to moving the center of gravity higher, but looks the most balanced whatever that means.
I wish I was using some sort of compact quad engine that is chain driven, has reverse, electric start and a built in CVT. (My grandkids are too young to deal with shifting.)
Anyone aware of a Quad that has these features in the 13 hp range?
Thanks
Herman

herman pahls
06-08-2016, 04:23 AM
I crash tested the almost completed 13 HP Predator powered mini buggy I am building for my 9 year old grand daughter tonight.
And no one was driving it.
I had just finished bleeding the brakes and decided to use a piece of welding rod to operate the throttle by hand since the foot throttle is not yet designed.
It was running and I decided to go get a helmet for its first drive.
When I came back a minute latter it was gone and no where in site.
I live on a steep (in 250 feet from my shop there is 100" drop in elevation) wooded hill and this is not the first time something has rolled away.
Years ago my 73 Chevy PU was totaled when it hit the only tree that would stop it from landing on the county road.
I have had tires/wheels disappear and had to search the jungle to retrieve them.
You would think I would learn my lesson by now.
Sure enough, it slalomed past several huge trees and over brush and center punched a small tree with no damage to the 1" diameter by .083 tube on the nose.
Two feet either side it would would have done a nice 20' vertical dive onto the county road and I am sure the frame would have been tweaked.
I retrieved it and drove it back up the hill into the shop.

I am struggling with how to hook up the throttle on this 13hp Predator.
I did a 6.5HP Predator a while back and it was easy in comparison.
I am by passing the governor.
The throttle butter fly on both the 6.5 and 13 turn counter clockwise to open.
They differ on what side of the butter fly pivot the push/pull rod attaches.
This reverses the direction on the 13 HP and makes the throttle lever with the cable attach points not useable as I see it, or as I did on the 6.5 Predator.
Any photos or descriptions of how other 13 hp Predator users did their throttle with out the governor?
I would post photos but have no clue how to.
Thanks
Herman

tazmannusa
06-08-2016, 12:56 PM
For kids I would leave the governor intact and just hook the throttle cable to the arm the way it's setup for from factory, works good and easy to limit top speed-rpm's. Mine are setup that way, even the vw I am putting together has a rev limiting rotor in it

herman pahls
06-10-2016, 03:37 AM
TazThanks for the throttle advice.I had already removed the governor so decided to go without and ended up with a good feeling throttle by re-shaping the throttle arm.I have driven it several times for a few minutes and must say I am not as impressed with how it starts cold or hot as compared to the 6.5 Predator.The 6.5 often needs to be choked even when hot and immediately idles clean.The 13 HP has a hard time deciding if it wants to idle and takes several tries.I have the idle turned up to the point the CVT is starting to engage.Acts like it is lean on the idle circuit.I have been so busy getting the mechanicals sorted that I have not read the engine manual if it addresses these issues or not.Seems to run fine otherwise.Do you have any ideas or did you experience hot or cold starting and transition to idle issues?ThanksHermanIt seems to actually start better by rope than the electric starter.I am using the stock airbox, filter and exhaust.

tazmannusa
06-10-2016, 12:57 PM
I kept mine pull start and it starts easy but cold it runs like it has a race cam in it for the first minute or so , I had to keep the idle on the low side because the 780 clutch engages at 1700 to 1800 and the kart would lunge when starting . Your's sounds like it may have a little junk in the jets try cleaning them out, I had to do that on a friends when the engine was new out of the box and now after getting a lot of hours on it , it's broke in good he said he doesn't have to choke it to start warm anymore . eventually I want to get the after market carb that has the adjustable idle jet

herman pahls
06-22-2016, 03:55 PM
Taz
Just back from vacation and wanted to continue the Predator 420 discussion.
The engine now has several hours on it and runs well.
When warm, I found that it will start with a little throttle or choke.
Seems like these engines are jetted on the lean side in the idle rpm range and an after market carb with more adjustability would solve the mixture issue.
Which carb do you have in mind and where would you source it?

Regarding idle rpm.
I do not have a tachometer, but it seems this engine needs to idle quite slow to keep the CVT from wanting to engage.
I am using a BMI clone clutch and a Comet driven, 7/8ths wide belt.
I have a hunch that this clutch is wanting to engage at a much lower rpm than your 780, which is requiring too low idle speed for good starting.
I am having regrets that I did not spend more on the CVT.
Do you have any idea what your idle rpm is?
I will take the carb apart to check for dirt.
Thanks again
Herman

ProtoDie
06-22-2016, 05:12 PM
you can try moving the clutches closer together to compensate for low idle engagment.
you may sacrifice a little of the full range on the clutches but it works

tazmannusa
06-22-2016, 09:58 PM
This is the carb I am thinking about getting
http://www.vegascarts.com/product-p/tunedcarb.htm
I'm not sure what the exact rpm's are so I just set it so the clutch was not pulling , my wife's with the china 40 series kicks in at a little higher rpm but the thing with that one is about every 10 to 20 hours of use I have to take the driver off clean and service then it's good again, it will get to the point it won't disengage or downshift, I tried a different driver and it did the same , hills, heat, and dust seem to be the culprit. If yours is engaging to early it may be that it's sticky and not disengaging all the way IE there is a bushing- spacer at the outer end of the large spring when it starts getting stuck on the shaft it won't push the clutch back to idle position

herman pahls
06-27-2016, 04:53 AM
Jody
You suggested moving the clutches closer together.
What distance are you suggesting from the comet suggested center to center distance? 1/8" , 1/4" ?

Taz
I am also using the China series 40 Driver from BMI (and a Comet 44D driven) and my grandkids got a whopping 3 hours use before the driver would not return to idle.
I took it apart, could not see any dirt/sand, sprayed some lubrication (which probably attracts dirt/sand) and it started sticking again right away.
Can that bushing spacer that you referred to at the end of the spring be modified/improved since you have a lot more experience with this problem?
When you said you tried another driver, was it also a China version or a Comet?
Is there some sort of machining/modifications that can be done to the China 40 series or Comet 40 series driver to make them reliable or is it time to get the Visa card out and step up to the Comet 780 series or the CV tech CVT that Jody at Protodie sells?

My 6 and 9 year old grand kids are having a great time with this minibuggy except when the Driver will not release which is all the time now.
I appreciate this forums help.
Herman

ProtoDie
06-27-2016, 10:17 AM
its fine tuning your clutch engagement go 1/8 closer and start from there and check it

tazmannusa
06-27-2016, 12:15 PM
The first time I just lightly used emery cloth to smooth things out. Do not use any wet lube , use the black dry lube stuff. The other one I tried was a china one also so I can't say if the comet one has the same problem or not. Strange is the spiderbox that I converted over to the 420 and china 40 has no problems but the engine is setup for half speed .
There are some U tube video's on how to clean and lube them.
Did you use the comet FNR ? if so how do you like it

herman pahls
06-27-2016, 05:01 PM
Jody
Thanks for the insight on where to start on fine tuning the CVT.
Just to let you know, I am pleased with how those Empi coil over shocks you sent me are working out.
I used them on the rear and have them set up to give 12 inches of wheel travel.
I was concerned at first that they might not have enough dampening which is not an issue for my 50 pound G-kids when they jump this thing.
At half the price of Fox's and less weight, the Empi's are a bargain.

Taz
I ordered a Comet 40 series driver from BMI today and complained about the generic 40 they sell.
Hopefully it will work out better.
I am using the Comet reversing box and it is nice to have reverse when the G-kids bury the rear end in the sand when they do not make it up a hill.
I am curious how well the reversing box will hold up to the shock loads from jumping and the whoops.
Since the CVT is slightly loading the gear box, it is necessary to momentarily kill the ignition to make a shift.
My only concern for now with the gear box is that the shift lever has a lot of slop and does not have a nice crisp feel with detents like one would expect.
Not sure what I expected for $250.
I am looking for a reversing option when I do a build using the Honda 630 V-twin since this box will not be up to the task.
Thanks
herman

herman pahls
07-08-2016, 10:00 PM
I drove my G-Kids 13 HP Predator powered mini buggy today to test the Comet 40 sized Driver that replaces the BMI generic that would not release at idle after only a few hours.
They look identical except the Comets large nut is welded so it appears it was not intended to take apart like the generic is.
I kind of fit by removing their kids seat and moving the pedals all the way forward.
They love driving this thing (ages 6 and 9 and 50 pounds) but I came away disappointed in how the 13 hp runs in comparison to the 6.5 predator that powers their smaller buggy.
For a lack of a better explanation it acts like it is CONSTIPATED and it may be since it has the stock exhaust, carb and air filter.
It acts like it is not breathing or has a huge flywheel.
I am waiting for a Trial Tech tach (got the idea from Jody's newest build) so I can monitor the RPM's and determine if the gearing is way off (if anything I feel it is geared too low according to calculations and it is geared much lower than Dain254 geared his ).
The 6.5 has stock exhaust and carb but I placed a foam air filter and had to drill out the main jet so it would not bog on acceleration.
The 6.5 rips with a CVT.
I found performance kits at affordablegokarts.com and nrracing .com
Any ideas on getting the 13 hp Predator 420 to wake up?
Thanks
Herman

darwinpayne2000
07-11-2016, 01:10 PM
I just read through this thread and I have a few thoughts to share.

A stock 13hp engine with the governor removed should have a fair amount of power. I know that the 10hp buggy I bought years ago with a Comet 500 CVT had a 6:1 ratio and 20-inch tires. My current buggy has a bigger engine and 22-inch tires, but I run an 8:1 ratio (primary/secondary jackshafts). That has been working well with my setup.

The carburetor may also be part of the problem. To boost the performance on my buggy, I went through a series of carburetors (B&S 14hp V-Twin). The modified carb that you alluded to earlier will probably make a big difference. You might also check out the carbs offered by affordablegokarts.com.

On my engine, the stock carburetor was pretty anemic. I substituted the carb from an 18hp V-Twin and that started to wake up the engine. As I built up the engine, I kept going bigger on the carb. Now, I'm running a 34mm Mikuni with a custom intake manifold and I'm getting about twice the horsepower out of it.

I am also running the classic Shredder II suspension with the dual chains. It works great on narrower buggies, such as my single-seater, because you don't need to worry about accommodating the width of a pair of CV axles. The chain setup is critical, however. I had issues with the dual chains coming off until I got the setup tamed. If I have a moment, I'll take a picture and post it.

Lubricating the clutches requires a dry lube that is, essentially, teflon spray. I bought a can back when Comet was still in business and one can lasts a really long time. The Comet spray is still available. Do a google or ebay search and you'll find it.

So, if you're looking to fix the performance on your engine, check your gearing and swap out the carb. :o I think.

herman pahls
07-13-2016, 04:21 AM
Darwin
Thanks for the info. and taking the time to respond.
I also am using the chain drive down each trailing arm with a combined ratio of 6.45 to 1 with 20" rear tires.
Were you using the Clone 13 HP predator?
I ask because it seems like you had a build with a V-twin.
Before I go any further with the 13hp Predator, I am concerned about the very annoying intense vibration this engine puts out.
Is the vibration normal, am I doing something wrong or did I get a lemon.
I emailed nrracing.com regarding the vibration and he said a Honda 390 was night and day smoother and a much better engine.
Nrracing also said a flywheel and crank could help the vibration.
Would an aluminum flywheel help smooth the Predator?
Is the carb mod all you did to your 420 Predator?
Stock exhaust?
I am willing to scrap the Predator engine if someone can advise me that that is a good move.
If I consider the Honda 390 then why not go with a Honda or Briggs V-twin?
Are the twins considerably smoother than the singles including the Honda 390?
I have enough effort in this build that I hate to short it with a less than desirable engine.
Thanks again
Herman

tazmannusa
07-13-2016, 12:27 PM
I can say yes the Honda is a heck of a lot smoother running engine, The wife's GX390 is a lot better than the 420 but it was more than double the $ without electrics. I found the the bad eye ball shaking vibration usually come from the chains, smaller sprockets, larger chains and high RPM's. Add a little jack shaft and axle flex and it magnifies, I found keeping the chain adjusted on the snug side when cold and well lubed helps

darwinpayne2000
07-13-2016, 07:40 PM
I'm running the B&S V-Twin these days, but I started by playing around with a Tecumseh 10 hp engine. Right now, I have a Tecumseh 8 hp engine on my minibike. The path for getting more performance out of an industrial engine is basically the same, regardless of the brand. For example, I put a clone Honda GX390 carburetor on the Tecumseh 8 hp motor and it made a world of difference in performance. It was actually better than the small Mikuni round-slide that I tried on the first go-around. In your case, a modified GX390 carb would be an easy upgrade and help address any carb-related issues with the Predator engine.

I also looked at nrracing.com to try and understand what he was saying about a new crankshaft and flywheel to fix the vibration issues. The Predator engine is half the price of a GX390 for good reason and that may be related to some vibration in the engine. An upgraded (e.g. Honda) flywheel would certainly help smooth the engine. I would also assume that their crankshaft has a better balance and would further reduce vibration, but the crankshaft is $100. I would try the Honda flywheel for $20 and see that that gives you. An aluminum flywheel usually has the opposite effect. It's lighter and allows the engine to rev up quicker, but also fails to dampen vibration as well.

Another option is to mount the engine on some rubber, like a piece of conveyor belt, You need to be careful, however, because you don't want the engine moving too much when the clutches engage.

My Tecumseh 10 hp engine had rubber mounts, but when I built out my buggy with the B&S engine, I went with a really heavy mounting plate (5/16 inch) that bolts the engine and the primary jackshaft together as a unit. No muss, no fuss and it seems to absorb any vibration that would be generated by the engine and primary jackshaft. Scott, at ubuilditplans, always recommended a heavy engine mounting plate to help absorb vibration.

herman pahls
07-17-2016, 06:43 AM
Thanks to Taz, Darwin and Jody I am starting to solve some vibration issues.

I do not have body panels but found that the floor panel was the source of a lot of vibration.
Even though the drive chains to each rear axle were not coming off, removing all the slack with chain tensioners reduced the vibration even more.
The 420 is now more tolerable to drive but far from being electric motor smooth.
Thanks for confirming that the GX390 is way smoother than the 420.
I like the $20 idea to try a 390 flywheel and possibly the 390 crankshaft.
How about a 390 connecting rod ?
Assuming these parts will directly bolt into the 420, for $150 I would have the Honda rotating assembly and possibly the less vibration of the Honda.
Another $30 and the idle mixture adjustment of the Vegas carb.
Am I thinking clearly or is it time to bail on the 420 and bite the bullet on the GX390?
As long as I am considering upgrading to the GX390, why not go with a B&S V-twin.
Darwin, please tell why I need a V-twin like you have.
I found a B&S 18HP on Amazon for $1060 including shipping.
The main negatives of the V-twins are having to come up with an exhaust and a fuel tank, which are non issues once you have already built the buggy from a pile of tubes.
Are the V-twins really night and day better than the singles?
They are not that much heavier or larger in size than the 390/420 so retrofitting should be easy.
Please help me decide which direction to spend my VISA dollars.

Do I need a shrink?
Why is a 64 year old messing with lawn mower powered mini buggies when he has a turbo'd Subaru sand car and a Hayabusa powered road race car?
I have a kick driving this thing even though it is for the G-kids

darwinpayne2000
07-17-2016, 05:43 PM
I would take it a step at a time. For example, you've eliminated most of the vibration by reworking the floor pan and tightening the chains. The cost for that was essentially zero. Get the flywheel and see what difference it makes. It may be close enough that you don't need to spend the extra $$$ on a new crankshaft. Same for the connecting rod.

I've really love my V-Twin engine and it makes a killer sound, almost like the rumble from a V-8, but it's probably more engine than what you need for your grandkids kart. Plus, a few tweaks to those industrial engines makes a big difference. Try the carburetor update with the new flywheel and see what you think of the performance. That's the route I would go first before starting over with a new engine. The fun is with the tinkering, you know. :o

herman pahls
07-18-2016, 02:25 AM
Darwin
Thanks for trying to spared my Visa card but the V-twin is for me.
I plan to build another buggy that fits my 6'-2".
I will order a stock GX390 flywheel as you suggested.
Is the carb that Taz suggested on post #101 from Vegas karts preferable to a stock Honda GX390 carb for use on the 420 or are they the same product?

Regarding the V-twin.
Are the B&S twins preferable to the Honda's because of more aftermarket performance parts?
Any suggestions of what muffler to use to prevent ear splitting noise.
What do you think about the Amazon B&S 18HP Twin selling on Amazon for $1060 including shipping?
Or should I consider the 20 or higher HP models?
thanks again
Herman

darwinpayne2000
07-21-2016, 12:43 PM
The modified carb from Vegas Karts would be preferable to a stock Honda GX390 carb for your Predator engine. It's been modified for better performance, plus you have the ability to adjust the idle mixture. On my minibike, that came in handy. It ran much better after I adjusted the screw out a bit. While you're at it, you might pick up the modified woodruff key for the flywheel to advance the spark slightly. Every little bit helps.

As far as V-Twin engines, I would go for the B&S over the Honda, simply because I know that you can get every imaginable performance part you need from Performance V-Twins. You also want to go with the 20 or 22 hp engine over the 18 hp engine. The 14 - 18 hp engines use the "smaller" block, like mine and most of the performance parts are made for the larger block engines. The 20 and 22 hp engines use a 1" keyed shaft, which is more common. Some of the larger B&S engines use a larger shaft and clutch choices begin to narrow. If you go with the V-Twin, you'll also need to go with a larger set of CV clutches. I use the Comet Duster clutch setup and it works fine, but there is also CVTech, etc. With greater horsepower comes greater (aka wider) clutch belt. :) You would be looking for a set of clutches that use the 1 3/16 or 1 1/4 inch belts.

The stock muffler on a B&S Vanguard is pretty quiet compared to the noisy animals I have on my engine. I wear ear plugs most of the time. :D Back Water Performance Systems stocks larger mufflers that are probably quieter.

Once you start down this path, your Visa card can take quite a hit, but you can get a pretty good bang for the buck if you:

Remove the governor
Install the rev kit
Install the modified B&S carburetor sold by Performance V-Twins

High compression pistons, Mikuni carbs, etc are all available, but they require more tinkering with the engine and put you in the "4 hours in the shop for every hour on the trail" mode.

tazmannusa
07-21-2016, 02:12 PM
Yep I have thought about switching mine over to the V twin a few times but talk myself out of it. The buggy handles good and drifts nicely with the 420. Built it around the 420 with 780 clutches with no extra room. The V twin would fit barely but I would have to install fuel tank above it plus a battery adding considerable weight .
If I do anything I think I would buy the 460 cc from Vegas carts ,rated at 25 HP or build mine with stroker crank and cam . The one from VC would be nice but it doesn't have charging system behind flywheel. But then the gran kids come over and ride the heck out of it and love it the way it is so why mess with what works

herman pahls
07-21-2016, 04:09 PM
Taz and Darwin

I sure appreciate the combined knowledge your guys have with the 390/420 and the twins.
Your info. helps my decision process.
The Vegas carb is on the way.
Affordable go karts advised that switching to the Honda 390 flywheel may not improve the vibration from their experience plus nrracing said I will need a UT2 coil to go with the 390 flywheel.
Apparently there is more to the swap than a $20 Honda 390 flywheel unless you have experienced otherwise.
I am considering going with an ARC racing #6622 flywheel, even though I realize it will vibrate more than stock.
Nrracing website warns of possible serious injury if you use the stock flywheel with the governor removed.
The #6622 offers timing adjustment.
Any opinions on the ARC lightened flywheels?

I am still considering the 18 HP B&S twin, even though it is a small block with little performance options.
I would get the smoothness of the twin and not have to modify it like the 420 needs to move an adult around faster.
Also, I could possibly still get away with the Comet 40 series CVT and the Comet reversing box.
Good or bad reasoning???
Thanks again
Herman

darwinpayne2000
07-21-2016, 08:13 PM
If you want to try the ARC racing flywheel, then give it a go. I wonder what nrracing knows that we don't know about the flywheel on the Predator engine? Maybe it's related to the vibration? Who knows?

The B&S 18 hp engine uses the same rev kit as the larger displacement engine, so you can still wake up the engine and get more performance out of it. However, the carburetor options are more limited. I think you must go with the dual Mikuni setup if you don't use the stock carburetor. Maybe that's a decision for down-the-road.

I assume you're thinking of replacing the Predator engine with the V-Twin and using the 40 series clutches? That should work if you're mostly riding on flat or maybe hummocky ground. I moved the Comet 500 clutch setup from the Tecumseh 10 hp engine over to the B&S V-twin and it worked fine except when I tried to climb a steep hill. The belt would slip and lose some power. I talked with Scott at ubuilditplans and he's the one that steered me to the Comet Duster driver/driven clutch. It solved the problem.

So, if you're thinking of a new build and you need to purchase clutches, then I would strongly recommend the 780 or Duster clutches with the 1 3/16 inch belt. Bigger belt--better grip. If you're upgrading the existing buggy, however, then use the 40 series clutches that you already have.

herman pahls
07-22-2016, 08:14 AM
Darwin
I went to the performance V twin website and noticed the rev kit mentioned but no details of what the kit includes.
For now I am not interested in the rev kit if I go with the 18 HP B&S since the 40 series CVT and Comet reversing box probably should not be subjected to more than 18HP.
I am so pleased with how the chassis and suspension turned out that I do not want to short change the project with a engine i do not care for.
So curiosity killed the cat they say and eventually my intrigue with the V-twin will make a dent in the credit card.
I blamed all this on seeing dain254's post of his build a while back and I had to try a mini buggy.
I am glad I did.
When the 6 year old G-kid outgrows the 6.5 Predator buggy I will build another mini and consider the 20-22 Hp B&S and go with the 780 series which I should have in the first place.
Thanks
Herman

darwinpayne2000
07-23-2016, 12:20 PM
The rev kit doesn't include very much, but it does offer a good bang for the (somewhat expensive) buck. You get upgraded push rods, a shim to go underneath the valve springs and a Woodruff key that advances the spark.

Most of it is self-evident. The shim is a copper washer that stiffens up the spring so the valves won't suffer from valve float when you rev up past the stock 3400 rpm's. The push rods are heavier duty so they won't bend from the extra pressure required to push the valve down. The Woodruff key is offset so you can adjust the flywheel and advance the spark a little bit.

herman pahls
08-02-2016, 04:07 AM
I installed the Vegas carb today and am very impressed with the results of having an adjustable idle mixture.
Out of the box it starts way better than the stock carb for both cold starts with the choke and hot starts no longer need the choke or messing with the throttle.
Before I had to grind away with the E-start for several tries to get it to light up, now you momentarily hit the E-button and it starts and idles cleanly immediately.
The Vegas carb came with a smaller main jet than the stock Predator main jet so I swapped them.
The Vegas carb appears to be identical to the Predator carb except the main jet size and adjustable idle mixture.
That probably explains why I did not notice any difference in top end performance.
Spending $30 for a night and day better starting engine was well worth it.
Possibly the only negative is that the engine does not seem to idle as slow as before with the idle speed screw completely backed out.
Does anyone know what RPM these engines idle at?
1400-1600 rpm ?

Herman

tazmannusa
08-05-2016, 12:31 AM
Thanks for the report on the carb, I need to order a couple of them . I never did hook up a tack on the 420 or the 390 so I can,t say what the idle rpm's are.
Does the comet 40 driver work better smoother than the generic one ?
Been working on the wife's , tore it down sandblasted and one coat on the chassis so far , thought about upgrading the cvt sense its apart but it's a bit much more surgery than I want to do

herman pahls
08-05-2016, 05:44 AM
Taz
I did not drive the generic driver to comment on smoothness.
The G-kids were driving it and only got a few hours before it would no longer disengage.
The Comet driver works great, I have several hours on it but no time in the dunes which should be the true test.

herman pahls
08-08-2016, 05:46 AM
I wish the Comet reversing box worked as well as the Comet CVT's.
From my limited experience (10-15 hours) with the Comet reversing box I would not use another unless I can figure out how to make it perform better.
I was concerned before installing the box with how much slop there was in the shift arm.
I spoke with a comet tech advisor and he said that was normal and by design had to be that way.
For the first few hours it was driven without shift linkage and it never slipped out of gear.
Even with very light weight linkage I have to bungee the shifter in forward or it will pop out of gear on a regular basis.
The shift action is not linear from neutral to forward or neutral to reverse so a positive locking shifter like Protodie sells would need to be modified.
It is a challenge to shift for me and almost impossible for my 9 year old G-daughter, so a fix is needed.
I will say that it shifts better on hard surfaces like dirt better than on a high drag surface like sand which is where it spends most of the time.
When i shift it I do the momentary engine kill method to take the load of the shift fork and that helps the shift.
The engine idle speed is low enough that the CVT is not trying to engage.
That is asking a lot out of a 9 year old.
It is getting harder to shift with use, so it is time to take it apart and see if there is a fix and probably be on the search for something else.
I like having neutral(when you can find it) for the ease of pushing it around because of the drag on the belt on the rotating driven.
Is it me, the install or a low quality reversing box?
Any experience or advice?
Herman

Wheels
08-09-2016, 11:58 PM
I was actually planning on using one of those for my son's build. I believe I will hold off until you give a report on whether it can be adjusted/fixed. looking forward to your findings Herman.

Ironleath5
08-10-2016, 06:04 PM
I purchased one of those over a year ago from BMI carts and I am planning on using it in my sons build as well. I took it apart when I first got it and I wasn't real impressed with the way it looks. At this point I'm seriously considering trying to build a forward neutral reverse gear box with an 8 to 1 reduction

herman pahls
08-10-2016, 06:54 PM
Wheels, Iron and anyone else using or planning to use the 16HP Comet reversing box.
Your results may vary.
This is what happened to my Comet FNR.
It would no longer shift so I did an autopsy on it and found a destroyed shift fork and I am at fault.
How is that for a confession.
I called BMI today to see about the cost to replace parts and if too expensive I will buy a new one.
I feel the box can be easily modified to prevent what happened to me.

The issue is that it would slip out of gear, so I used a bungee cord to keep it in gear. BAD MISTAKE
The bungee places constant tension on the shift fork and it destroyed the fork and exposed the bearings to a nice slurry of metallic oil.
Now that I know how the gearbox functions I would have done things different so I am not ready to trash the idea.

I have been road racing motorcycle powered cars for years.
When the transmission starts to slip out of a gear on a regular basis that means the shift dogs have started to get rounded and it will only get worse.
The only solution is to replace the dogs and in some cases the after market will machine an undercut in the dogs so they in essence lock in place and will not release till the pressure is off the dogs.

The Comet Dogs only engage about 3/32" which is not very much. Less than 1/8".
I will use a dremel and a small 1"diameter abrasive disk to undercut the Comet dogs and I expect that issue may be solved.
The undercut will be about 3 degrees and should take only a few seconds each to cut. There are 6 dogs, 3 on each gear.

If you use the box as is, I suggest making a locking mechanism that keeps the shifter in forward.
Jody at Protodie sells a locking shifter but it will need to be modified since the distance from forward to neutral is different than from reverse to neutral.
The ball/spring detent system is marginal so it is difficult to find neutral at times.
Make sure the locking device takes all the slack out of the sloppy shift fork but does not place a continuous load on the shift fork.

I feel that the box should give much better service if these simple precautions or modifications are made
I will keep you posted when I get it back on the dunes for the G-kids

If you have a Comet box you want to sell, please let me know. I need one right away
Herman

tazmannusa
08-15-2016, 04:08 PM
the generic one on the wife's started to bind up again after about a days use so I took the other one apart that only had a couple hours on it, nasty had like a gummy grease on the main shaft where the spring and 2 bushings ride with wear and scratches already.I guess we get what we pay for, this last set I payed a $100 on ebay .
I think I am going to have to invest in the comet one been looking at the 44 magnum vs the 40 but I just don't know if the 44 is a better unit or not.

herman pahls
08-15-2016, 10:01 PM
The 40 series Comet driver that I replaced the BMI generic with has been working great for 10 hours.
Most of that time has been in the sand. which I consider a bad environment for anything mechanical.
Only got a few hours out of the generic

herman pahls
09-01-2016, 06:55 AM
I replaced a bearing and the shift fork in the Comet FNR box and drove it today for the 1st time since the rebuild.
It works well and did not slip out of gear. YET!!!
Since I undercut the dogs, the gear box resists popping out of forward (like it did before undercutting) unless you let off the gas to take the pressure off the dogs.
I had destroyed the shift fork by using a bungee to keep it in gear even after a few hours of use.
Also the bearing that aligns the input and out put shaft with each other was no longer recognizable.
It is a tiny 12 mm ID bearing and that is why the instructions insist that the input/Driven shaft be supported with an outboard bearing which I had done.
Also, what were they thinking designing an output shaft with only one bearing and no easy way to support it with a 2nd bearing.
As much as I like having a FNR gearbox, I will look for an alternative for the next build even if it costs 2-3 times as much.
Before I buy another FNR box it would be nice to know if the input and output shafts are well supported with 2 bearings each.
Your results may be completely different than mine or maybe you and your G-kids do not know how to "break an anvil with a rubber hammer like we do".
I will keep you potential Comet FNR uses posted on how the gearbox holds up.

The next move is to try fitting the B&S 16 hp V-twin, if it will fit with out major engine cage mods.
The extra power will be a good test for the 17HP rated FNR.
I got to find out for myself if V-twins are the answer.
Herman

herman pahls
10-19-2016, 03:48 AM
Continuing drama with the Comet F-N-R
I thought I had solved the issue of the Comet FNR popping out of forward by undercutting the 3 drive dogs.
The buggy ended up going on a week long off road trip and it performed well in comparison to the RXR 170's the other kids had.
I got a kick out of my 9 year old G-daughter specifically thanking me for putting a reverse in the build since she said reverse got used a lot on the dirt trails they were on.
No sooner did they get home we went out to the sand dunes and the Comet FNR failed again by being stuck in neutral
The autopsy revealed that the gear that gets moved by the shift fork to engage F or R was bound up on the keyed 3/4" shaft in neutral.
There was plenty of oil in the box and had to use a hammer with moderate force to drive the gear off the shaft.
I decided that there was not enough clearance between the gear and shaft to get enough oil, so i sanded it on the lathe to free it up to hopefully prevent it from seizing again.
The dogs that i had undercut were already looking like they were rounded and likely to start slipping out of forward anytime soon.
The box seems leak oil from the gasket, so this time i assembled it with silicon only.
This required some minor machining of the main shaft to allow the case half's to come together since the gasket is quite thick.
I also found a 3 pound compression spring that fits on the main shaft and am hoping this spring will help keep the dogs engaged.
I feel the spring could easily be a 6 pound spring.
Now the concern is that the spring will keep the FNR from staying in neutral or reverse.
I may have to build stops in the shift lever for this reason.
Remember, your results may be completely better than mine have been, and you may not have any issues.
Next time around I will consider a Polaris FNR that cost about the same on E bay.
Mad Minion has been successful with his on a heavier and 100HP (Suzuki 600) build so it should last forever on 13 HP.
The Polaris FNR will take a whole lot more work to install and be able to use Comet style Drivens on.
I will report on how this rebuild and mods hold up.
i do not give up easy.

65chedderbob
10-19-2016, 11:10 AM
The latest remodel of my build was centered around a Polaris FNR, and a few things I have noticed with how I have it set up are that it does have a shift lock built into it so you need to pull a second lever back and lock in place before it will allow you to shift. However, we have a bit of stiction in the cable we are using to disengage the lock so the return spring doesn't always pull the lever back 100% so it may pop out of gear. We tried a stiffer spring, but then we couldn't pull the lever far enough to disengage it. It would likely be fixed with a happy medium spring.

Also, with the way we have the mass of bent linkages and multiple pivots for the shifter, it is so short throw it is very difficult to find a gear without skipping over it. I need to change the lever lengths and pivot points and this should be solved as well.

Otherwise, the Polaris HRNL has worked wonderfully

herman pahls
11-09-2016, 11:57 PM
65cheddar
Thanks for sharing your shift linkage issues you have had with the Polaris FNR.
I took some measurements of the FNR from a Polaris quad I found at the dealer.
It would require a total revamping of my drive train to retrofit that FNR since it is several inches taller than the Comet.
I will consider the Polaris FNR for the next build.

I have spent more time modifying some of the internals of the Comet FNR and seems to be working well and shifts much easier than when it was new.
Once you have reverse it is hard to go without it.
herman
After having reverse

herman pahls
11-24-2016, 03:11 AM
Regarding Mikuni pulse fuel pumps.
For safety reasons I have decided to remove the stock Predator gas tanks on my G-kids 6.5 and 13 HP mini buggies.
I had a fuel cap start to leak and gas was dripping all over the place ( the gas really sloshes on rough ground) so I grounded the buggies till I came up with a fix.
I ordered go kart style between the legs aluminum tanks from BMI.
Since there will no longer be gravity feed to the carbs I also ordered Mikuni pulse pumps and the pulse port manifold that bolts between the carbs and cylinder head.

I am looking for advice as to where the best place to mount the pulse pump.
I have read that the shorter the pulse line to the pump the better.
Also they sell aluminum plates that bolts in place of the stock gas tank that the pulse pump and throttle linkage then bolt to.

Does the pulse pump need to be mounted rigidly to a similar plate to work properly?

Thanks
Herman

Xbird
11-24-2016, 12:30 PM
Hi herman, i ran a mikuni pulse pump for awhile on my 250, the smallest (i think was a VM 44 or 41 model iirc) also required the use of a regulator because the rate overcame the float needle and i could not get one suited to match it. Led to continual flooding at idle. Something to be aware of.

The closer to the carb, the better and yes, securely mounted. I bolted a piece of flat aluminum to my gas tank framework and put the pump and regulator on that. Rubber washers between the pump and plate wouldn't be a bad idea just to stave off an potential for cavitation from vibration.

darwinpayne2000
11-29-2016, 01:23 PM
I would second the advice on using a regulator with the pulse pump. I have a pulse pump on my engine and I started having flooding issues with my Mikuni carburetor. I installed a new float valve seat and needle, but that didn't fix the problem. I later learned that you need a smaller diameter on the float valve if you're using a pulse pump. The carburetor originally came from an ATV that used a gravity feed, so I had to order a different seat/needle (1.5 vs 2.5) to fix the problem.

herman pahls
12-01-2016, 04:53 AM
Darwin
Makes sense that gravity feed would require a larger diameter seat/needle and that fuel pump pressure could over come a larger diameter seat/needle.
I assume smaller diameter seat/needles are not available for the 6.5 and 13 hp Predator engines.
I was hoping someone would tell me where to access a regulator that is appropriate for the Predator engines with Mikuni pulse fuel pumps.

Xbird
12-01-2016, 06:31 PM
try to find lowest pressure adjustable regulator possible. i used one from the auto parts store (purolator) and ran it on its lowest settings with restricted feed lines to get it to work.