g9 rebuild

[lady bug]

Can anyone explain to me if I order a standard size piston for my 285cc motor will this go right in my cart with out any boring basically I was told stock piston size is 73.00mm and I checked my stock cylinder hole and I have a tight 73.00mm so I don't know how this will fit because you need at least 3-5 mm piston to wall clearence

[sho305]

If you have a stock bore (should be measured with a mic) then yes the piston will work, you should hone the cylinder and put new rings on the piston. Problem is why do you need a piston? If the walls are worn this is not a good way to do it, though it can work and people do it all the time. The walls and the rings both wear and you are repairing only half that wear. It would need to be bored oversize and an oversize piston fitted to have a new bore with full compression, then it would run like new. Assuming you have a wear issue is why you need a piston.

G9 lists a .03-.05mm piston to wall clearance spec, that is .0012-.0020 inches. You need to be able to measure that.