Single disc bully clutch

I bought 3 used clutches and 2 were pretty rough looking. Found the 3rd in decent shape, air gap around .035, disc is about .125, doesn't look like any shims are left. We tested it down the road and it seemed ok. Took it to the track and made about 4-5 laps in the heat when the son pulled over unable to run anymore, engine still running he says it wont go. Swapped back to the drum clutch we had been running and finished out the night. I just checked everything again and noticed the inner edge of the weights have been ground down. Am i just to the point where it needs a disc or is something going on with the weights? I thought i should've been able to get a couple nights out of it based on measurements on bully website but knew it was pretty close to the end.
 
Your air gap and friction disc seem to be within spec. and spring heights ok.
You say the clutch has weights; brass weights on each lever?
Some are radiused/undercut to make it easier to service them. Also, the weights could be hanging up against the pressure plate or actuator lever plate preventing the clutch from full lock-up - maybe someone had changed the radius on the weight levers themselves, or there is some other issue that the weights were ground on (don't know without seeing it in person.)

Was the clutch simply not engaging? Did it get extremely hot for 5 laps of running (indication of slippage)? Key was in place?
Also, if there were no shims and a new friction disc installed (.125" is = to new disc thickness), then it is possible that the center splines of the clutch needs cut to tighten the air gap up on the next rebuild.


-----
?Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
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30 years of service to the karting industry
Linden, IN
765-339-4407
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Yes the brass weights have the lower portion ground off. I touched it and quickly removed my hand due to how hot the clutch was when he pulled off/over. I will get some pictures tonight and double check my measurements on the disc. It seemed wore on one side more than the other so I don’t believe it would be new. Yes key was in. He was leading until the issue.
 
Everything seems pretty flat. Let me know what you think if anything looks out of wack. We had a motor problem at the same time and i just changed them both out. But like i said when i touched it coming off the track it was 400 plus i would say. He did spin about two lap before this happened so i'm sure that heated it up too.
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All looks fine to me other than it's glazed up pretty good.
The brass weights are clearanced like that from Buller. That is fine -- just makes it easier to disassemble and keeps the edge of the brass weight from catching on the edge of the actuator lever plate when they swing out.

I assume it worked fine for a while since you said he was leading when the problem occurred. The spin may have caused some heat, but shouldn't have made the clutch too hot to touch.
I'd suggest cleaning it up good, hit it lightly with some 80g paper, soak in acetone, and re-assemble. Set the air gap between .030" & .050" (whatever your preference) and try it again.

Double check the engagement as well. It should be at peak torque for your engine/class.
 

flattop1

Dawg 89
6 .010 shims ? I don't remember ever seeing that many on one .
Also don't see what the original airgap was .
The floater and hub look pretty bad too me , hopefully cleans up good .
The assembly bolts didn't come loose by chance ?
Ok .035 .
This is 2 different clutchs , one single disc and one 2 disc ?
 
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No its all one clutch. See the numbers at the top of my picture and add 1 silver to that it was stuck on and i didn't notice it when i was making my notes, noticed it tonight going back together so originally had 4 gold 4 silver. I took out two golds, scrubbed disc and put it back together at .035. The bolts sure didn't seem very tight when i was taking it apart but this is the first time i've taken one apart. I'm thinking my original measurement was off on the air gap cause after taking two golds out i'm at .035 now.
 
The gold shims are only .005" ea, so that would have put your original air gap only slightly wider @ .045."
Now, be sure to check your air gap at several points around the clutch. A variance of more than a couple of thou. is a problem and will require regrinding the pressure plate and backing plate.
 
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