Torque that clutch nut !!!

[Larry S]

My grandson and I went for a ride. I had him on my CW and I was riding my SR. Half way through the ride, the clutch on the CW went out. Grandson was upset that he broke my bike. I assured him that he didn't break anything - he was just riding it when it broke.

The next day, I pulled the clutch case and found the clutch nut laying in the case. The entire clutch (with the exception of the fiber plates and springs) is scrap iron.

[Bullfrog]

Bummer! (and use loctite too)

Ed

[matt glascock]

Good news - lots of those available for replacement. Just curious: was the clutch wired or assembled with nylock nuts?

[Larry S]

It was wired.
Larry S

[matt glascock]

Probable wouldn't have made a difference here. I'm trying to figure out what happened. Was it that the clutch nut simply loosened up and fell off?

[hodakamax]

Yikes! What a disaster! Never had that happen. The nut does require big measured LH torque and should have a bend-over locking washer. I blame things like that on DPOs but things do happen as I can attest. Egad! Maxie

[Larry S]

Yes Matt. The clutch nut loosened up and fell off.

[Bullfrog]

Ouch! It makes my head hurt trying to imagine the chain of failure which would result in the damage shown in your photograph. Example: One thought was that the clutch would start to "drift" off the end of the crank splines . . . and the screw ends would start hitting the clutch cover components . . . BUT WAIT - the clutch disk/spacers/pressure piece would hold the clutch from sliding "out". Hmmmm, try another thought . . . oweeee, I have a headache. NOTE: I've never seen a failure like that before.
Ed

[taber hodaka]

I wonder if it could been a clutch bolt failure? PABATCO made part number 202500 the kit fit all models 100 - 125 including the combat wombat. Label says super strong clutch bolt kit. if one bolt let go the rest would follow and the nut would be loose?? Clarence

[Bullfrog]

Clarence (and Larry ),

I keep bumping into the "need" for simultaneous "faults" (which would be highly unusual). It does look like all but one (the first one to fail??) of the clutch screws came apart at the end of the shank AND got "pretzeled". I don't see any damage to the threaded ends of the screws (which, again, makes my head hurt). It doesn't seem like failed clutch screws could loosen the clutch nut . . . and I've not yet been able to imagine how a loose clutch nut could cause the screws to fail. Yep, the headache is coming back. (But it is an interesting puzzle!)

Ed

[Larry S]

The clutch nut is striped. I think it happened while it was coming off. It was new when it went on.

[thrownchain]

I’m not sure the nut coming loose would cause the screws to fail, and the idea that all 7 screws would fail at the same time is a bit much. The screws look like they were broken by lateral torque like when you break a bolt off over-tightening it , possible? Or they were loose before ? And play in the clutch assembly broke em?

[Larry S]

No. When I rebuilt this engine I also rebuilt the clutch with new metal and fiber discs from Terry. The screws were safety wired.

[Larry S]

What I think happened - the clutch nut came off. My grandson rode it until it wouldn't go any further.

He is young, and had never ridden a two-stroke. The engine could grenade under him and he wouldn't know.

[matt glascock]

In the picture of the clutch nut, the back half of the threads are intact while the front half are "machined" away entirely. The clutch cage is keyholed and all the screws are fractured in the exact same way suggesting the pack was intact when it experienced instantaneous deceleration to zero. I can see the clutch nut spinning off as the first domino to fall, but what caused the "machined" out effect on the clutch nut. Also, what was the condition and position of the safety wire when you pulled the clutch cover? Sorry to keep beating this, but I'm sure I'm not alone in wanting to know how to avoid pictures like you've provided. Yikes. I'm also interested to know if the pros on the forum think the shock loading incurred here warrants opening up, inspecting and rebuilding the motor.

[Larry S]

The safety wire was pristine. After I removed it, I easily backed out what was left of the clutch screws.

After some clean up and polishing with the Dremel I think I can salvage the hub and cover.

[viclioce]

I wouldn’t trust any of those clutch pieces. You can’t guarantee there aren’t micro-fractures in them you can’t see. I would start fresh. Hoping your crank threads aren’t damaged too! Victor