by Enaud90 » Sat Dec 14, 2019 12:47 pm
How the piston is/was marked depends on who manufactured the piston. I have 55 NOS Harley pistons left on the shelf and a few Welworthy and Heplex (both English) pistons. A number 3 or 30 or .030 would indicate the piston is .030 oversize.
However, the 3 standard NOS Harley 125 cc pistons I have do not have a size marked on them. All the oversized ones are marked 5 , 10, 20, etc. The later NOS Harley pistons are marked .010, .020, etc. The reproduction pistons made
by Egge (USA) for J & M are very well marked and there is no question as to the size as it is very distinct.
Duane Taylor