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View Full Version : Not a buggy, but gasoline powered and Kid related...



iflytii
11-30-2017, 12:42 PM
A good friend of mine gave my son a pretty sweet mini-bike a few months ago. It was his old pit bike, and something my son has dreamt about riding for years as he would go sit on it and make motor noises every time we visited the shop. Took a couple months to get enough time to get it all together but after new tires/tubes, and a rebuilt carb, we had it ready to run this past Thanksgiving at Grandpa's house.

https://photos.smugmug.com/Thanksgiving-2017/i-XrJN6Ns/0/1077525f/X2/Mini%20Bike%20Pre-Crash-X2.jpg (https://iflytii.smugmug.com/Thanksgiving-2017/i-XrJN6Ns/A)
https://photos.smugmug.com/Thanksgiving-2017/i-F9pFktM/0/a5c1027f/X2/Mini%20Bike%20Pre-Crash2-X2.jpg (https://iflytii.smugmug.com/Thanksgiving-2017/i-F9pFktM/A)


We quickly discovered a few things that we will need to address. The obvious is getting a clutch cover on this bad boy as after a low-speed tumble, it did a pretty good job on my son's left leg. The not so obvious thing is doing something about the clutch itself. Because of the "chopper" style, the bike is really front end light and the clutch doesn't engage until at least half throttle where it then jerks and almost pulls a wheelie. This led to the accident after getting into an oscillating motion (on-throttle, off-throttle, on-throttle, ground) as he was turning down onto the "downhill" section of Grandpa's track. I suspect the clutch is original to the bike and is probably just worn enough it's taking some extra rpm's to get it spinning fast enough to engage. New clutches are pretty cheap but I was curious if anyone here has any experience or recommendations with clutches that engage at lower RPM's? Most of the cheap centrifugal clutches I've found don't seem to have any info on what RPM range they operate in. I might just be over thinking this and the $13.95 clutch I'm looking at on Amazon will be fine but thought the experts here might have more insight.

K-fab
11-30-2017, 07:43 PM
I remember those bikes. Seems like they had ads in the back of Boy’s Life for them.
Bummer that it bit him. Guess that’s part of having a bike, eh?

Enjoy!

darwinpayne2000
12-01-2017, 12:59 AM
I looked at mfgsupply.com and the Comet centrifugal clutches engage at either 2000 or 2200 rpm. Other clutches are probably the same.

I would suggest trying the centrifugal clutch first. They're relatively cheap and a new clutch may fix the engagement issues. I have a minibike that I adapted to use a Comet CVT setup and it's a fair amount of work. Basically, you have to shoehorn a jackshaft into the frame, which means that you have to move the engine forward and also reverse the rear wheel to put the sprocket on the opposite side to work with the sprocket on the new jackshaft. A fair amount of work.

Another thought. If the front end is light, can you get a new chain and move the engine further forward?

Edit: I had forgotten about the Comet Torq-a-verter. It's a simple method for adding a CVT transmission to a minibike without all the work and fuss of adding a jackshaft. However, I would still try the centrifugal clutch first.

Xbird
12-01-2017, 02:30 PM
man that takes me back, had a bunch of old ones that came from sears wish list catalogs and rupps when growing up. Had a place, Red's scooter shop nearby. needed a clutch, just went and grabbed one off his shelf for less than 10 bucks with no thought about what it was. nearly took my head off on a pole anchor guyline in a field where we used to ride--think that might've been one of my last rides ever ....

iflytii
12-05-2017, 04:17 PM
I looked at mfgsupply.com and the Comet centrifugal clutches engage at either 2000 or 2200 rpm. Other clutches are probably the same.

I would suggest trying the centrifugal clutch first. They're relatively cheap and a new clutch may fix the engagement issues. I have a minibike that I adapted to use a Comet CVT setup and it's a fair amount of work. Basically, you have to shoehorn a jackshaft into the frame, which means that you have to move the engine forward and also reverse the rear wheel to put the sprocket on the opposite side to work with the sprocket on the new jackshaft. A fair amount of work.

Another thought. If the front end is light, can you get a new chain and move the engine further forward?

Edit: I had forgotten about the Comet Torq-a-verter. It's a simple method for adding a CVT transmission to a minibike without all the work and fuss of adding a jackshaft. However, I would still try the centrifugal clutch first.


I ordered a cheap centrifugal clutch to see if that helps. As cool as a CVT would be, we are about to start on his buggy around the first of the year. A friend picked up an abandoned project basically for the motor (ninja 600) and I'm getting the buggy part of it. It's just a cheap Chinese thing that needs a motor, and probably some re-working of the suspension as the front had been chopped off and a warrior quad suspension grafted on with bubble gum and spit. For the price, it has some potential, and if I'm doing a CVT on anything, it's going to be that project.

So for now, hopefully, a new clutch and some safety features (clutch guard and non-sticking throttle) will work but we will also concentrate on improving gravity averting skills too just to be safe. :-)