[Ken the Sec]

The most important thing about plain clutch plates is that they are perfectly flat and smooth. It's contact area that provides grip, any form or roughness will only create rapid wear. Replacing corks in clutches is a miserable task because they need to be sanded down laboriously by hand on a sheet of sandpaper on glass - a good job for criminals seeing as it usually leaves you without any fingerprints...
Obviously the clutch needs to be set up so that the pressure plate (the one that carries the springs) lifts level by adjusting the springs otherwise spring pressure will be uneven leading to both slip and drag, that sometimes explains why a  clutch is worse with new plates but my guess would be that the new steel plates aren't quite flat. Depending how they are made they may have distorted slightly. I would try the sheet of glass using, this time, emery paper to see if they polish up evenly across the whole surface.
I always sand new friction plates this way too because they are rarely completely flat. Like brakes they will wear in over time but it's better to start with a perfect surface if possible.
cheers Rick

Many thanks Rick for a very comprehensive and useful reply.  I'll see how it beds in and if still not good I shall follow your suggestion of emery paper on glass.  Then I can install the 3 flattest of the 6 plates I now have, and also get the outside plate as flat as possible.  Ken

[Rick Parkington]

The most important thing about plain clutch plates is that they are perfectly flat and smooth. It's contact area that provides grip, any form or roughness will only create rapid wear. Replacing corks in clutches is a miserable task because they need to be sanded down laboriously by hand on a sheet of sandpaper on glass - a good job for criminals seeing as it usually leaves you without any fingerprints...
Obviously the clutch needs to be set up so that the pressure plate (the one that carries the springs) lifts level by adjusting the springs otherwise spring pressure will be uneven leading to both slip and drag, that sometimes explains why a  clutch is worse with new plates but my guess would be that the new steel plates aren't quite flat. Depending how they are made they may have distorted slightly. I would try the sheet of glass using, this time, emery paper to see if they polish up evenly across the whole surface.
I always sand new friction plates this way too because they are rarely completely flat. Like brakes they will wear in over time but it's better to start with a perfect surface if possible.
cheers Rick

[phutton]

Yes Ken, I now use a semi-solid grease!

P

[Ken the Sec]

Just a thought - what oil do you use in the gearbox? I had a similar insoluble problem, traced eventually to using an EP oil in the 'box.

P.

I use a semi-fluid grease in the gearbox.  A little comes out of the other end of the gearbox and wets the final drive chain (not a bad thing!) but there does not seem to be any leakage at the clutch end.  I will look for that next time I take the case off though.  Thanks Paul.

[kbryt]

EP oils????in old bike gearboxes?

what a subject to rile folks with.... I just avoid the topic  and use loads of old fashioned grease with graphite additive in all my old boxes.

[phutton]

Just a thought - what oil do you use in the gearbox? I had a similar insoluble problem, traced eventually to using an EP oil in the 'box.

P.

[Ken the Sec]

I have had intermittent clutch slip problems over the years with my 1928 Model 6, usually fine for riding but not enough grip for the kickstart.  I have attributed this to too much oil normally but a good clean recently did not improve things.

So I got one new corked plate (to replace the most soiled one) and 3 new pressure plates (the old ones are a little pitted), plus new springs, and rebult the clutch with these, having cleaned the old parts with Gunk.  It was worse!  So I took it all apart again and cleaned the new plates too.  I also lightly abraded the corks on emery cloth using a pressure plate as a holder.  Still very poor.  So I put the old pressure plates back and GERONIMO!  At least until I tentaively put a little light oil in the case.  Another story - I thnk I shall run dry in future and just apply a little oil to the chain.

So what was I doing wrong with the new pressure  plates?  Should they be abraded to improve grip or will this just increase cork wear?  And before you ask - yes I did check the pushrod free play at each stage!