International Lancia Forums

Can someone please tell me what is the proper bore. I assume it is 21mm. I understand there are, maybe, 4 different sizes. Is there an issue with using any of the four?
Are the kits readily available?

there should be an alloy tag wrapped round the cylinder near the mounting holes which says. Normally 21mm. I think there were 2 othere sizes 17 or 18mm??

Tim