Does anyone have any experience of fitting a J Knibbs BSA Cadet Major piston seal, I have obtained one but am having difficulty fitting. The leather washer has been cut on an angle, the long side being 6mm above the short side when looked at in profile. The fibre/rubber backing washer is 22mm (7/8) massively undersize on a 1" 25.4mm piston.

I feel that if I level up the washer I may be able to fit but the washer would be unsupported and thicker on what would have been the longer side..

Please share your collective knowledge?

Ormicron