Vintage Dirt Bike Q & A

I just bored over the jug on my MT250 and an installing a Wiseco piston. The instructions that came with the piston talk about drilling two holes in the piston skirt. What is the purpose of that, and do I need to do that? My original honda piston looks very much like the Wiseco piston and has no holes drilled in the skirt.

You drill 2 small holes on the EXHAUST side of the piston, ONLY if you have a BRIDGED EXHAUST PORT.
This is to aid in oiling of the birdge so you dont lock the ring up on it. OR you can relief the bridge so there is a few thousants clearance between the ring and the bridge.

_________________
1994 AHRMA National Champion Sportsman 125 Intermediate.
1996 AHRMA National Champion Classic 125 Expert.

Thanks. That makes sense. Since there's no exhaust bridge, I won't have to worry about it.

You are correct, no bridge, no drill. Enjoy

_________________
1994 AHRMA National Champion Sportsman 125 Intermediate.
1996 AHRMA National Champion Classic 125 Expert.

Just curious - is there any harm if you drill even though the bridge has been relieved?

_________________
osu_cowboy

You can, for extra insurance.

_________________
1994 AHRMA National Champion Sportsman 125 Intermediate.
1996 AHRMA National Champion Classic 125 Expert.

Thanks!

_________________
osu_cowboy