I was wondering what the bore is on a stock trailblazer 250, I think it is 72x60 stroke. Also, for a 250 2-stroke what would the boring size(mm) have to be to make it a 300, 350, and 400 etc. I know there is some formula for the conversion of bore size to cc's like, bore squared x pie x stroke x number of cylinders, but not sure if thats the right calculation.