A clutch project

[zrx1100]

Off and on, the clutch on my bike has been acting unreliably in the friction zone. When slipping the clutch as the engine revs, the clutch would sometimes let go somewhat and then grab again. It only happens once in a while, but it is enough to be annoying and distracting, especially in the hilly San Francisco. I have replaced the clutch plates, measured steels for warpage (not warped), and have only used conventional oil since engine rebuild. The only issue I can see is that the boss and the basket have wear marks. I have been reading that the wear marks can act as ramps for friction and steel plates to slide on and create problems similar to what I am experiencing.

So the other day, I got this gem on ebay: an NOS clutch basket! Also have a boss to match on the way.

@gggGary, @Jim, others, what else should I plan on replacing when swapping the basket? Roller bearing/plate, spring washers, thrust washers?

 

[Jim]

Unless you're experiencing some other problem, I don't think I'd change anything else. The clutch is one of those things that are relatively easy to get to, so swapping parts later on isn't that big a deal.

Oth... Mikes XS sells a thrust bearing with a lot more needles than the OEM one. I've read others say it's a good part. Prolly my first plug for Mikes ever.

 

[5twins]

Yes, that MikesXS bearing is a nice upgrade simply because, as Jim said, it has more rollers in it. It will not "fix" any clutch issues like they claim, lol, unless maybe if your original bearing is worn out. I put one in my bike and saw absolutely no difference in the way the clutch operated. Obviously there was nothing wrong with the original bearing I replaced, lol.

 

[gggGary]

Does this have the 8 plate clutch in it?

 

[zrx1100]

Does this have the 8 plate clutch in it?

It does. This was happening before I put the 8-plate in it.

 

[gggGary]

It does. This was happening before I put the 8-plate in it.

And still?
cuz the 8 plate changes where the plates hit the basket so should kinda stop/ reduce any catching?
Usually not needed but bump up to stiffer springs?
have you scuffed the steels?

 

[zrx1100]

yes, indeed, the 8-plate stack contacts the basket and the boss in different places, but can still ride on sloped areas. I do have stiffer Ferodo springs. It could also be something else. maybe the thrust bearing. I did scuff the steels.

 

[gggGary]

Hmm, strange. IIRC The reported symptom of notchy fingers is sketchy release. something stopping the pressure plate from applying the spring pressure? All I've got. Will be interesting to see how installing the new hub goes.

 

[zrx1100]

one thing I have not tried is checking the worn areas for smoothness. there could be a few areas that are just light notched and catch a plate from time to time. The bike runs great, so will wait untill some rainy weekends to start the project.

 

[zrx1100]

the NOS boss has arrived:

 

[zrx1100]

Opened up the clutch today. Nothing super obvious other than maybe some wear on the boss. The basket is actually not that notched. A bit of pitting on the pushrod. Not sure how much pitting is tolerable.

@gggGary you can see where the steels from the 8 plate vs 7 plate engage with the boss.

 

[zrx1100]

So, unfortunately, the new clutch boss turned out to be a 256-16371 and not 341-16371 (as it was listed on ebay). So ended up just putting the old basket and boss in. The basket is in good shape. On the boss, i just knocked down so sharper marks left by the steel plates with a blunt pick. Also repaced the throw bearing with the "upgraded" one from Mikes and put in all new steels. Also switched to a single-piece pushrod as I did not like some of the pitting on the sections of the OEM one. Will see how it all hangs together over the next week.

 

[zrx1100]

After 200 miles of testing, the conclusion is that the clutch works great! None of the unpredictable slipping or grabbing during engagement. I’m not entirely sure what solved the issue, but my leading suspect is the pushrod. The old two-piece rod had asymmetric pitting from the bearings, and I can see how that could change the effective length as the segments rotated and shifted in those non-circular pits during engagement.


It could also have been the steels. The old plates were flat enough that a 0.006" feeler gauge wouldn’t slip under them on a glass surface, but who really knows. I’m still running gggGary’s 8-plate clutch, and Ferodo springs and everything feels very solid. So not much of a project in the end.