Gruve in cylinder

[Custom200]

In my 1981 rm 250 there is a small gruve in the cylinder. i am getting it bored but what will that gruve do...all the boys say it will be horrible but dont know what will happen??????

[Kilborg]

The whole reason you are boring the jug out is to remove the imperfections of the sleeve. I have had to go as far as .020 over on a few topends to get them back within spec.

Unless the grooves are running well into the cylinder you should be fine. If not, a resleeve is in order.

[Custom200]

is there a amout i can get it bored to where the stock piston will still work??? Sorry if my questions seem dumb but this i my first 2 stroke rebuild and well i not really sure about boring and stuff.

[Custom200]

ohh and thanks for the imput

[RedRider_AK]

Nope. Any bore job will require a new piston. They usually sell pistons for popular machines all the way up to .100 over, or at least .080 over.