That's the information I needed, Paul. Thanks very much. I'll take the cylinder to a machine shop now and see what size piston it will need after it's bored out enough to clean it up.

Tom

Thanks for the info. I guess I should let a machine shop tell me what size piston I need too. I just thought that there might be some mark on this piston to tell me whether it's the original (factory-stock) size or not.

Tom

I've torn down my Ace 90's engine for rebuild, and I'm trying to find out what size piston it has. The bore is no longer round, the ring end-gap is about a quarter of an inch, and the piston is scuffed up and grooved, so I'll have to rebore and go oversize on the piston. Trouble is, I can't tell wha...

Thanks Jack. I'm no machinist, so I'll probably end up sticking with the four-speed.

I'm still curious to know what has to be done to make a 5-speed fit.

Tom

My Ace 90 has started making a terrible clatter in the gearbox. It sometimes shifts with a crash, and the transmission now rattles in every gear at one throttle setting or another. Therefore, it's time to split the cases and see what's going on in there. As long as I'm going in there, I wonder if it...