piston sizes

[catch me if u can]

is there any way to tell what size the piston is by the numbers on the top of the oiston

[Paulie B]

Well what I've seen with Yamaha motors is theres 2 different ways to tell. Some I've seen tell you how much the over-bore is ie .25, .50, .75.
And the other way I've seen is the exact bore size in mm like 83mm or 85mm.

[outtacontrol250r]

yea you can exactly what he said ^^ if its a weisco it will be in mm like say if its stock it will say 66mm on the top of it thats for a 250r

[catch me if u can]

it is a pro-x 310 and the numbers are 10560m07225 and that is right across the center of the piston i was wondering if the last 4 digits were the piston size(7225)???????

[outtacontrol250r]

yes it is its 72.25 mm which is a 310 piston