Drilling holes in the piston.

[RM125CCF]

Do most Wiseco pistons come with the holes already drilled on the exhaust side or do i have to do that myself? If so what size holes? Bike is a 1991 Rm125 I ordered top end kit from mxbike.com

 

[souphmars]

mine have always came with the holes already drilled

 

[psycho]

I have an '03 CR250 and have to drill the holes in the piston. The instructions that shoud come with piston state the size and location to drill the holes. Been a while since I did one and don't remeber the size. If you still can't find the size, post again and I will do some diggin when I get back home.

 

[RM125CCF]

Whats the purpose of the holes to relieve exhaust pressure or heat?

 

[RM125CCF]

actually now that i think about it my old piston had an arrow pointing to the exhaust side so maybe when i get it in i wont have to drill holes because thats the only reason i see the exhaust side having an arrow for.

 

[CR500pilot]

If the install directons say to drill it, then drill it. I don't know if its required on that bike, but I have done it before and its not a big deal. The holes are to cool the exhaust port bridge.