[Steve_M90]

Through a process of trial and error I have an understanding of the key parameters. For the corks in the sprocket and the two thinner plates, too much cork is an issue - the outer plain plate won't engage (see photo 1 below). For the outer thicker plate, too little cork is an issue - the spindle that operates the clutch will touch the gearbox input shaft and stop the clutch closing any further.

So I ended up with these size corks: sprocket = 7.3mm, thin plates 5.5mm and thick plate 9mm.

I think I have also found the issue causing the wear in the first place - I bought some new plain plates and these have a mirror finish making the old one looking pretty rough.

Many thanks to Andy and Quae at The Clutch Cork Carvery for their helpful service and prompt turn round.

[Rick Parkington]

I think I would agree, thickness of lining is not as important as contact area and i have found that replacing plain plates for new (properly flat) ones can be more successful than renewing apparently worn fibre plates - assuming there is still material on them but one thing that has just occurred to me is that, thinking of fuel tap corks, it's essential to soak them in boiling water before fitting, which makes the cork incredibly soft and pliable and causes it to mould to  the correct shape and thickness when it cools. If you did the same with the clutch cork plates, I wonder if they would squash down so that they fitted, flatten themselves evenly against the plain plates and even sort of rivet themselves into their holes. It's not something I have tried but I will next time because I can't see it doing any harm - you could strip it the next day to make sure the water hadn't rusted the plain plates - and if it's anything like as impressive as it is with the fuel taps it will make a huge difference.
Cheers Rick 

[kbryt]

take a bit off the friction material, I found its the amount of friction that matters, not the depth of it.

Cork plates mostly need renewing when the cork gets hard or glazed.

That's what I have always found to be the case anyway.

Years ago some friction plates only had a sliver of cork on them, Triumph/BSA I think it was.

[Steve_M90]

1932 Model 90, left-hand clutch release, foot change.

I have had my clutch plates recorked by Andy at The Clutch Cork Carvery, a nice and quick service. However, despite special consideration, I have the same issue as with previous rebuilds – the assembly doesn't allow sufficient engagement of the outer plain plate with the centre piece (see photo 1). Overall the assembly seems adequate as the outer corked plate easily engages in the sprocket (see photo 2).

The various plates and corks have the following dimensions:

Sprocket cork thickness = 9.3mm
Thin plate (2 off) thickness = 2.4mm, cork thickness = 5.5mm
Thin plate (1 off) thickness = 3.5mm, cork thickness = 5.9mm
Plain plate thickness = 1.75mm

Sprocket cork thickness = 0.37"
Thin plate (2 off) thickness = 0.09", cork thickness = 0.22"
Thin plate (1 off) thickness = 0.14", cork thickness = 0.23"
Plain plate thickness = 0.07"

In the spares book it gives two dimensions, 2 corked plates at 7/32" (5.5mm or 0.22") which Andy has used for the thin plates and 1 corked plate at 23/64" (9.1mm or 0.36") which Andy has used for the sprocket. He made the corks on the thick corked plate marginally larger.

Previously I have sanded down the corks on the thick and thin plates but this has always seemed irrational as I'm deliberately using up clutch life! I am now wondering what size the corks should be on the sprocket as it is these corks and those in the thin plates that determine the insertion of the final plain plate in the centre piece.

Is there anyone with a similar experience?

Thanks

Steve