Hi,
I've been dismantling my M20 for rebuild
The engine has a brass tag marked bore STD.
The top of piston is marked 826.
I see conflicting info online.
I haven't mic'd it up yet
Does 826 mean standard bore.
Tnx
Patrick in NY
Is it a BSA piston or an aftermarket item?..The standard BSA piston (M20) has part number 66-1190 marked on it to denote a standard size...Oversizes are numbered with a similar series of numbers...Standard bore size is 82mm...82.6 isn't a standard marking but 82.5 would be plus .040" and would be found on an aftermarket piston...Ian
