Page 7 of 9 FirstFirst ... 5 6 7 8 9 LastLast
Results 61 to 70 of 81
  1. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #61
    Senior Member
    Join Date
    Sep 2017
    Location
    Lincoln, Nebraska
    Posts
    124
    Default
    I guess before you do more engine work, I would advise you improve the front suspension so you can see more speed improvements easier. Just my opinion.
    Reply With Quote
     

  2. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #62
    Senior Member
    Join Date
    Sep 2014
    Location
    West Palm Beach FL
    Posts
    903
    Default
    Quote Originally Posted by darwinpayne2000 View Post
    As far a spinning some donuts, etc, when I'm out at the sand dunes again, I'll grab some video of the buggy in action.
    Reply With Quote
     

  3. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #63
    Senior Member
    Join Date
    Sep 2017
    Location
    Lincoln, Nebraska
    Posts
    124
    Default
    I kind of hope Performance 670 makes a stroker crank for the 670 at some point or at least offer mods for other engine lines, ARC Racing only offers some of what I'm looking for.
    Reply With Quote
     

  4. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #64
    Senior Member darwinpayne2000's Avatar
    Join Date
    Jan 2010
    Location
    American Fork, UT 90 minutes from the sand
    Posts
    790
    Default
    I spotted this video on Youtube showing a rebuild on the Predator 670 engine using parts from Performance 670.

    https://www.youtube.com/watch?v=142ruxycPwo

    I think this was more of a demo on how to swap out the camshaft, connecting rods, pushrods, etc. If he was really serious, he would have dumped the stock carburetor for the 34mm Mikuni. As he stated in the video, the stock carburetor runs lean and there's no quicker way to burn up an engine than running it fast and lean.

    As far as my project, I've been busy with outdoor projects around the house. Trying to get the yard winterized. I'll get back to this as soon as I can.

    In the meantime, here's a picture of my brother-in-law burying the rear-end into the sand up to the top of the rear tires. He never does anything in half-measures.
    Attached Images Attached Images
    Reply With Quote
     

  5. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #65
    Senior Member
    Join Date
    Sep 2017
    Location
    Lincoln, Nebraska
    Posts
    124
    Default
    If I recall that was for their first 670 Buggy that burned to the ground because of a fuel line that leaked onto the exhaust. Then there's Vasily Custome Build's who had his throttle cable stick and sent him full throttle into a house. He switched to dual Mikuni clone carbs because of that. With RBG, he's switching to dual carbs for his larger mini buggy with a supercharged 670, I believe.
    Reply With Quote
     

  6. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #66
    Senior Member darwinpayne2000's Avatar
    Join Date
    Jan 2010
    Location
    American Fork, UT 90 minutes from the sand
    Posts
    790
    Default
    So, I got the yard winterized, then Christmas came along, then New Years, etc. Next thing I know, its February.

    Time to get back to this project!!! One of the holdups was a broken rear axle on the buggy. I took it for a final ride in late November and one of the axle bearings on the left side broke and took the second bearing with it. The whole axle came off and went rolling away with the tire!! Fortunately, it was on a trail wide enough to take my pickup down and load it up.

    The brake rotor was destroyed and the rear brake caliper damaged, so I replaced both rear rotors and calipers. Everything is looking good now. The rotors are slightly larger, so that should add some stopping power.

    The next step is to replace the muffler. Over the fall and winter, I agonized over the best approach for a new exhaust system. Should I just duplicate the existing muffler setup, but just have a rear exhaust? Go with the dual muffler design I had on the old engine or try and build some type of header with a new muffler. Buy a muffler or make one from scratch?

    Part of the problem is space. On a minibuggy, everything has to be "mini". The existing muffler setup is compact, but I wasn't convinced that it had the best exhaust flow. The headers sold by Bullfrog and others are fairly elaborate and would probably hang outside the buggy frame or wrap up over the engine where the new carburetor and air filter sit.

    I did some reading on exhaust headers and the true "performance" headers are designed to create a vacuum on the exhaust cycle of each port to suck the exhaust down the tube. Calculating the tube length and diameter to achieve this effect involves some math that's beyond my 4-function calculator. Besides, most of the "headers" sold for these small engines are not true headers, but just free-flowing exhaust systems. No real math involved.

    I finally settled on a "compact" header design, where the header tubes are connected directly into a side-intake and exhaust muffler. I came across a paper published in some technical journal that described how to design a compact, side intake/exhaust muffler that would achieve maximum noise reduction for the size of the muffler. The article included some formulas that I haven't seen since my calculus class in college so, again, that was a non-starter, but it included two helpful pieces of information. The intake and exhaust ports should be .6 times the muffler radius from the ends, which comes out to about 1 1/2 inches for my muffler design. Also, the intake and exhaust should be offset 90 degrees for maximum noise suppression. Works for me, so the intake will come in from the side, near the front, and the exhaust will point down in the back.

    I don't have any 1 1/4 inch mandrel tubing laying around, but I can make pie cuts on my band saw all day long. I cut up some tubing and welded it together to make a prototype exhaust. If it works out, Summit racing has some mandrel-bent tubing for about $9 apiece. I would only need two pieces to make this out of nice, pretty mandrel tubing.

    I'm working on the muffler right now. In the meantime, here are a couple of pictures of my progress.IMG_2352.JPGIMG_2354.JPGIMG_2357.JPGIMG_2358.JPG
    Reply With Quote
     

  7. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #67
    Senior Member darwinpayne2000's Avatar
    Join Date
    Jan 2010
    Location
    American Fork, UT 90 minutes from the sand
    Posts
    790
    Default
    So, forget everything I said about muffler design. When I went back and looked at the document, I had conflated some information from two separate technical papers. The numbers I pulled weren't valid for a side-inlet muffler.

    After looking at a few more muffler designs, here is my approach. The side-inlet mufflers all had the rear outlet pointing out the back, not the bottom, so I changed my design. I also designed it to have a baffle in the middle and a fiberglass liner to help reduce noise. The dimensions are:

    4 1/2 inch inner diameter
    15 inches long
    Dual 1 1/4 inch side inlets
    1 5/8 inch exhaust outlet

    I don't have one of those fancy roller machines that turns flat sheets of steel into nice, rolled cylinders, so I had to improvise. I went down to the local Ace Hardware and picked up a couple pieces of PVC pipe joints with a 4 1/2 inch outer diameter. I used the brute force method to roll the steel. Lots of hose clamps, to keep everything in place and a rubber mallet. The PVC pipe actually worked well because it would temporarily deform as I hammered, clamped and hammered again. The only mistake I made was not popping the PVC pipe out before the final clamp and tack weld. I thought the plastic pipe would slide out easily. It didn't. A few hammer blows later, it was out.

    The final steps were making a baffle plate, end plates and lining the muffler with fiberglass. I bought some metal screen material to use as a liner to hold the fiberglass in place. I formed it into a cylinder, wired it up to keep it from coming apart, then wrapped it with the fiberglass. It went in fairly easy.

    I tacked on the exhaust pipe and tried the muffler on the buggy for final fit. the straight-back exhaust was too close to my rear rack, so I cut it at a 20 degree angle to point it down and out to the side. That works much better.

    The final steps are to finish welding up the muffler, then attach it to the exhaust pipe.

    More pictures.


    IMG_2356.JPGIMG_2360.JPGIMG_2361.JPGIMG_2362.JPGIMG_2364.JPG
    Reply With Quote
     

  8. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #68
    Keeper of the Asylum K-fab's Avatar
    Join Date
    Jun 2006
    Location
    Scottsdale, AZ. 10.9 miles from the trailheads
    Posts
    10,331
    Default
    Very nice work and I love the innovation for the die.
    Reply With Quote
     

  9. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #69
    Senior Member kustomfab2003's Avatar
    Join Date
    Jan 2010
    Location
    De Pere, WI
    Posts
    147
    Default
    Nice work, thanks for the updates!!!
    Marine Veteran Sgt USMC 8151/8541 1992-2000
    Process Improvement Specialist Miller Electric MFG LLC
    CWI CWS CWE
    Reply With Quote
     

  10. Collapse Details
    Re: Re-engine Buggy with a (modified) Predator 670
    #70
    Senior Member darwinpayne2000's Avatar
    Join Date
    Jan 2010
    Location
    American Fork, UT 90 minutes from the sand
    Posts
    790
    Default
    Last night, I put the whole exhaust setup together. I welded everything up, fired up the engine, and . . .

    . . . it was quieter than I expected but also louder than I had hoped.

    It's not real loud. It has a nice, deep throaty growl out of the tailpipe. Great for impressing the natives, but I was worried that it would get a little tedious listening to it. On my old Vanguard engine, the exhaust was fairly loud and I had to wear ear plugs when I took it for a long ride.

    I had some extra tubing, so I decided to play around a bit. One piece of tubing was about a foot long with a 90 degree bend and it slipped slip right on to the short exhaust pipe. I popped it on and . . . almost total silence. I tack welded the tube onto the exhaust pipe and took it for a spin around the block. It wasn't much louder than a sewing machine. I knew that longer tubing would make the exhaust quieter, but I didn't think one extra foot would be that dramatic.

    This afternoon, I played around with various pieces of tubing attached to the exhaust pipe. If I make the exhaust 4 inches longer, it hits a sweet spot, where the sound in the front seat is relatively quiet when idling or driving, but it still has a throaty growl when you're standing behind it. I still need to impress the natives, you know.

    At the moment, I just have an extra piece of tubing tacked on to the exhaust pipe. I'm going to leave it for now. I need to take it out on the trails and decide if I have the sound level where I want it. I can add or subtract tubing as needed. When I find the right length, I'll cut off the existing exhaust pipe and weld on a new one at the correct length, using a piece of mandrel tubing so I can angle it down towards the frame. I think that would look better than having it stick straight out.

    Here's a picture of the muffler with the extended exhaust.
    IMG_2367.JPG
    Reply With Quote
     

Page 7 of 9 FirstFirst ... 5 6 7 8 9 LastLast

Similar Threads

  1. Mid sized snowmobile engine or Suzuki sv650 engine for buggy
    By Old fast guy in forum Motor - Engine
    Replies: 19
    Last Post: 12-05-2016, 06:01 PM
  2. Protolite MXT 22hp Predator 670 engine
    By ProtoDie in forum MXT - Kid's Buggy
    Replies: 13
    Last Post: 02-29-2016, 11:11 PM
  3. Modified ST2 Buggy - Rolling Chassis
    By uzrnaim in forum For Sale
    Replies: 15
    Last Post: 01-31-2013, 06:07 PM
  4. modified fl 440
    By buggyfreak34 in forum For Sale
    Replies: 3
    Last Post: 07-19-2011, 09:52 PM
  5. modified ody
    By b-boy in forum Show off your toys in here!
    Replies: 7
    Last Post: 11-11-2007, 11:28 PM

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •