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Clutch friction plates

Submitted by tom_mortensen on Fri, 11/05/2012
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This topic has probably been beaten to death, but having gone through old posts, I haven't found out what kind of plates others use in a belt drive primary case. So what do you folks use?

Up till now I have moved away from sintered bronze, which seemed to soak up oil like sponge, and on to Surflex fibre plates. They bite ferociously and never slip, but I have now discovered that after 3000 miles most of the plates are worn down, and friction material has turned the primary chaincase into a dust pit. I don't believe my riding style is very agressive, even though I never like to see any vehicle in front of me (cough, spit, ahemm), so I wonder if anybody has any other suggestions for friction plates?

Submitted by keith_glassborow on Tue, 15/05/2012

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I see no-one has replied and I can't really helpeven though my own assembly is a belt andSurflex. I haven't had the same wear and I am quite hard on take-off and thru' the gears sometimes. What I did experience was that the dogs that engage the clutch centre were worn to a tooth point. The clutch material also breaks off the dog area but that's it. First set which included some running with the chain lasted 20k miles. Currently the replacements are on 10k and have not started to showwear as before and as far as the surface is concerned the spiral reliefs seem as deep as when new. Have not measured the thickness.

Submitted by tom_mortensen on Thu, 17/05/2012

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Thanks Keith, I will have a closer look at my collection of friction plates. THe problem is that it wasprecisely the Surflex ones that turned into fine dust. Maybe foreign objects have entered the primary, and ground away the friction material. I also read a tip about the sintered bronze plates, indicating that reducing the friction area in a lathe could be a solution. At the moment the friction area goes all the way from edge of the plate to close to the centre, which is very different from the type that Norvil sells. Anyways, I will experiment a little more, at least I'm gettting familiar with the workings of this clutch, its actually a fine piece of engineering, light and precise when set up correctly. Thanks again for your thoughts.

Submitted by tony_ripley on Thu, 17/05/2012

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Hi Tom,

On the subject of thefrictionarea of the sintered bronze plates. I have a standard 850 MkIII with the original plates, new clutch centre as the plates had wornnotchesin it. I used to have to take the clutch apart every 2 or 3 thousand miles to wash the plates otherwise it slipped. I have now put them on the lathe and reduced the friction area by half. Since then I have done around 7000 miles without taking the cover off and no sign of slip. I would not know if they wear when run dry but so far after 65,000 miles there is no sign of wear oneitherthe steel or bronze plates.

Regards

Tony

Submitted by tom_mortensen on Thu, 17/05/2012

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Thanks for that Tony, sounds like this could be a solution, after all sintered bronze must bemuch more durable than friction fibres, no matter what the material.

Submitted by colin_sharpe on Fri, 18/05/2012

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Bronze plates were always a subject for discussion, even when the bikes were new. IIRC, the riders handbook and manual tells you to use Castrol GTX 20-50 oil in the primary case. Straight 20 Castrolite was supposed to improve things. There is also the problem of gearbox oil flowing down the gearbox main shaft and into the clutch, often caused by people topping up the gearbox oil with the bike on the side stand.

My 1969 S still has the original fibre plates which work well, I use ATF in the primary case.

 


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