Scooterotica

has any one ever used one?
thinking of trying in a sr barrel.

I suspect that the reason you haven't had a reply to this is because it is not a common motorcycle.

It would appear from the tiny bit of reasearch I have done, it has a 66mm piston. The standard piston has two rings, but the MX version only has one.

http://www.cmsnl.com/yamaha-ct1c-1971_m ... partslist/

As I don't know the compression height, the gudgeon pin size or whether it has reed valve holes in the skirt, I can't offer any more advice, but if you can furnish some more info, there maybe some advice to follow.

indeed 66mm standerd. 16mm pin.piston ported.30mm compresion hight.
drawn wire rings.cheep and loads available.twin ring.the weiseco version has a dykes top ring.gona try one. £25.00 including shipping all the way from the usa.