piston size

[blastermessiah]

i bought a motor with bad top end...it needs rebuilding. how can i check what size piston it currently has. does the piston have a number on it somewhere? how do i know if its the stock one? thanks in advance

 

[Whitty21]

there should be a nuber engraved on the top of the piston, always safe to measure it with a caliper though, always a good tool to have if u dont have one already

 

[Zwiser]

some pistons dont say like 66mm tho thell have a serial # that ull have to look up

 

[Awk08]

the only reason you need to know what piston size is if you are gonna bore/hone it yourself, you cannot buy a piston until the machinist bore/hones it to whatever size it takes to get the imperfections out of the cylinder
so just take it to whatever local shop you'll be using, or send it to ken oconnor racing, and they will let you know what size piston is needed

 

[Surfrjag]

if it has a bad topend it needs to be rebored so easiest to take it to a machine shop and they can measure it for you.

 

[blastermessiah]

well its not exactly bad...all it needs is to be honed. someone rebuilt it, kicked it over but had installed piston wrong and cracked the piston skirt. took top end apart and thats how it sits. i believe i can get away with just honing but i cant find a number on piston....is it on top or on the sides?

 

[Awk08]

number should be on the top,
but i've never heard of the piston breaking a skirt becuse of backwards installation, only bad piston slap, which would indicate it was too small for the bore ????
dont measure the old broken piston, measure the bore, that will tell you what piston is needed