Took apart my 1970 Aermacchi Harley 125cc engine and the piston is shot. I did some research and found the standard piston size is 56mm and apparently the stroke is 50mm. It is next to impossible to find a NOS piston for this engine but there are many 56mm 2 stroke pistons on ebay, most do not list stroke size. A lot of them look like they might work, but I want to be sure before I order something. Will another manufactures piston swap right in?