Clutch Install Problem

[David Chong]

Issue Summary:
KT100 PTO shaft seems too short to take a new clutch; drive sprocket baseplate binds with clutch against PTO chamfer when the starter nut is tightened.

Details:
I installed a new L&T 3 disk wet clutch for a buddy. Properly lapped, proper spacer, etc... I'm confident it was a good install and everything was in order.

He took it to the track and ran it without oil (yes... I told him he needed to fill it!). It promptly blew up, of course. Siezed and stripped all the teeth off of the drive sprocket.

I have pulled the old clutch, and have attempted to install a new clutch. However, when I tighten down the starter nut, even with no spacer installed the whole assembly binds up against the inside chamfer of the PTO shaft. There is no play whatsoever. Thinking it may be the clutch (wrong model, wrong taper, or something), I tried a third unit taken off a known working kart. It also slid on too far and bound, so it seems to be the PTO shaft.

Is the output shaft used up? There is no visible damage to the PTO shaft, and the woodruff key was intact when we took off the original smoked clutch. Is there anything I can do to mount a new clutch on this motor without a bottom end rebuild? How would the shaft have somehow shortened/changed since I put it together before the no-oil session? Like I said, the woodruff key was intact and the taper does not look ground down or anything.

Any help appreciated! Thanks,
David

[Jim Abbott]

David,
If you are over torching the starter nut that will happen. What are you torching the nut to?
Jim

[David Chong]

Thanks for the reply Jim. I don't think that's it. I'm torquing to 29.5 ft/lbs with a torque wrench, which works out to 350 inch-lbs. That works perfectly with all the other clutches I've installed on the other motors we have, and it has also worked with the clutch in question on a different motor.

On this motor, however, even with no spacer installed on the shaft , it locks up solid on the shaft.

[Geary Launder]

David,

The L&T manual only calls for 25ft/lbs. on the torque. Sometimes that extra 4.5lbs. can be the difference. Also, you want to double check that all your weight pins are properly installed. If just one of them is not properly seated it will cause the the weight and floater disks to bind giving the appearance of the clutch not seating properly.

Geary

[David Chong]

Thanks Geary. I'll take a look at the weight pins - even though I've been torquing to the Horstman spec, I still don't think that's the issue because it is already locked by about 20 ft/lbs. I am not particularly confident that it will be the pins, though, because I have tried two different clutches on it and they both had the same issue, and both of them work fine on a different motor.

[scmo777]

david, schannon here, if i recall correctly some clutches or drums of the clutches had to have a spacer on the shaft of the engine to keep the clutch from binding. i do recall having to do that with one of mine but i cannot remember if it was the horstman or the l&t. it has been to long to remember. the spacers were very small and had a taper that fit the crank shaft. you may try that.

[Geary Launder]

David,

One other thing to check is the hub. After submitting the clutch to that much abuse, sometimes the hub will crack. It is especially weak near the key way. I know this doesn't answer why it works on one motor and not the other, but it is another reason the clutch may not seat properly.

Geary

[David Chong]

I had Kenny throw the old hub away. The whole clutch went into the trash. Both of the clutches I have been trying to fit on the motor are brand new.

Goofy, huh?

[mikecampbell]

Hi David, our computer has been down for a while. All better now. I was hoping to offer advise on your clutch problem. I hope you figured out the problem before you tossed them. You may want to save your used stuff, one day some of it could save you some cash and get you through a couple of races. I have a "souvenir shelf" that is very useful sometimes. Thanks for asking for help at the track, I'll help when I can. We should pit together. See ya on the 14th.