I am not sure of the cylinder size I have at the moment and need to replace it and the rings.

Any one know the measurements I need to take.

The top of the cylinder has been de-coked a few times, so not many clues there.

Regards

Pat

email (option): sacombsashtrees@hotmail.com

Sorry. Meant piston sizes

email (option): sacombsashtrees@hotmail.com

If you clean the piston crown nicely, usually they are stamped something like STD, O/S 30 or +30. a magnifying glass and torch helps. Ron

email (option): ronpier@talk21.com

Hi Pat...A standard M20 bore is 82mm..BSA pistons are oversized in increments of +.020" and +.040"...(+1/2mm,+1mm)

Hepolite pistons were available in oversizes of +.010",+.020",+030",+.040" and +.060"...

I've had all of those at different times but oddly I've never seen a +.050" and don't know if they ever made that size...

The size of the piston should be marked on the crown....If you can't find it measure the piston on the thrust faces below the rings or better, get the bore measured to determine what you need. More so the latter if you are planning to rebore it...Ian

email (option): ian@wright52.plus.com