No, not really much to be gained by boring unless you buy a big bore kit. I think if you bore it, you cannot get yamaha pistons for it. It will cost you alot more to get it bored and finding pistons for it. If your cylinder is trashed, buy a used one. Better yet, the 97 and up 500 twin cylinders have much much better porting in them. More HP to be gained that way. I think you can peel the head gasket on these motors when your rebuilt it for more compression. Friend of mine had his 600 twin rebuilt and was told that the thickness of the head gaskets is rediculous. Just have to run premium if you do that.