B25 and the problem of suitable clutch plates

[Janner]

Forumites

I am struggling to find suitable clutch plates for my 1968 B25

The book says 0.168" thick across the wear material, when new.
I've purchased and returned 2 sets, both having been woefully under size.

The concensus seems to be Surflex
I've purchased a set of 4 Surflex plates and these, again, are woefully below standard.

Having perused the forum, I'm giving serious consideration to the idea of fitting 5 plates, rather than 4.

Can the forum offer me advice / pros / cons, for taking this step?
ANY advice will be gratefully received, this job is taking much longer than expected and I don't want to be in a home for the utterly bewildered, before the work is finished.

Thanks, as always

[rhyatt]

Have you tried Kidderminster motorcycles 01562 66679

[Janner]

I've bought and returned 2 non Surflex sets from UK suppliers
I have contacted 9 UK suppliers, asking for the dimensions of their friction plates including the dimension across the friction material
Those who repied ALL confirmed that their offering was below standard, one was 0.112"!!!

I contacted Surflex, apparently Brexit has created problems and they cannot ship to the UK . . . . . . Hmmmmm

If these Surflex plates I have here are below spec, what can I get in the UK, that will be in spec?

My feeling is adding a plate may be the most effective solution, but, has it been done on a B25?

[AltcarBob]

I had the exact same problem even the surflex plates are way under thickness. I stuck an extra plain plate under the pressure plate not ideal but it did bring the stack of plates up to the required thickness. I have kept the original friction plates and will eventually get round to finding somewhere that does relining.

[Janner]

Much as I want to keep the bike 'stock', this seems to be the only realistic solution

I'd figured out that another friction plate would mean another plain plate and the combined thickness would be too much
I'll fit the additional plain plate and like you, retain the original friction plates for future relining

[Janner]

Gents
I have the additional plain plate.

What does the current wisdom suggest regarding location?
Under the pressure plate, or at the back?

Thanks all

[rogerfastlane]

As the later clutch centre with the thrust washer also altered the drive hub (lip for rearmost steel plate removed) there will be a difference in the stack heights and/or maybe plate thicknesses anyway over the model years. With my early B44 motor I was using the earlier lipped hub with a plain steel plate at the back, but in my B50 it has the thrust washer/no lip design so can stack one more friction in there.
As the friction plates drive on their insert faces, and for normal use rarely wear, it is the number of plates that count, not their thickness (?) as the power is translated through the number of contact surfaces and this relates to the contact area provided by the number of plates.
The late type clutch used 5 friction and 5 steel plates while the earlier type had 5 steel and 4 friction. My original B44 friction plates are down to 0.12" and worked fine so after a clean and dressing the drive dogs will be popped back in. I would have thought a B25, unless running the early high comp piston/higher power may be happy with that sort of thickness as well - and this does seem to translate to having the right stack height to allow adequate clutch separation within the drum for clean gearchanges. I admit I would not want those friction surfaces to be any thinner though.
Pattern parts are sometimes the curse of the restorer and they are sold as if we should be grateful to get anything to fit - whatever the quality. I have had pretty good parts (but no clutch plates yet) from Feked.com - nice guys who will go the extra mile and will actually check parts if they have them, so if not tried yet, maybe give them a call?