Topic: CB750 clutch problem- Friction plate broken into 3 - Probably solved

[PeWe]

A friction plate has broken into 3. One small part had have a tour around the engine and caused a bad scratch in the lover crankcase half. Probably stucked between the crankcase and lower part of rod 4, followed it about 5 cm making a deep scratch.
I found it at the oil pump mesh where it hopefully has been most of the time.

The clutch is a cheap Heavy Duty with 8 friction plates and one extra metal plate.

-What is known to cause that?  Bad quality?
- I think it was a broken drive chain. (In that case it happened after max 2000km after installation)


- Other that have same experience?


The only event I remember is a broken drive chain on Autobahn.

The story about that event over 20 years ago.....
I did not adjust the chain in time (next gas stop) was close to become stucked behind a truck in an uphill, checked the other lane geared down 2 steps, 5th--3rd  and twisted the throttle, BANG!! the chain went off and we were happy to roll into a sidepocket where I waited to see oil flooding like a Halal event.... NO oil...good. A guy on a small motorcycle gave me a ride to next town  Kassel and I bought new chain, back and we could continue . Licence plate was cut in the edge like by a knife, chain guard went loose (finally went into a container in France).... I need a new chain guard now :-)

[PeWe]

Heureka! I know why now!
I got new plates and saw a huge difference compared with my earlier clutch friction plates. I'm disappointed with myself that I did not see that almost 30 years ago when I replaced the clutch first time, bought a  cheap Heavy Duty version with one extra plate. (extra metal plate too). The plates I have got before were all looking the same.
The latest plates now have one that has bigger tabs (wider) than the other and look different that I have read about in this forum. I have not however, seen anything about the tabs.

My clutch basket MUST have the wider tabs when the outer part has bigger distances for the tabs. The old plates had a lash of appr 2mm in the outer position in the basket, it must be why the outer plate broke. Both my kits got the outer plate broken, one tab off. Small nasty metal parts floating around in the engine, not that nice that can cost $$$.

Here a photo where this is visible, the outer plate with wider tabs and the other that match the basket very well this time. Halleluja!