The Hodaka Club Forum

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 what size this original piston is so that I can order a larger one.

I don't have a micrometer big enough to measure the piston diameter, but I was hoping that I could tell just by the markings on the piston whether it is stock or oversize.

Alas, there is no simple number on the piston such as 00, +10, +20, etc. What is stamped into the top of the piston is the number 75. Does that mean anything to anyone?

Tom

I had a similar problem. I solved it first, by determining standard size bore, and what over-size pistons were available. Then I took the cylinder to the machine shop and told them that the standard bore size is 48mm and which over-sizes you can get parts for and ask them to bore it to the smallest oversize possible according to available pistons kits..

Meaning I told him that the standard size was 48mm, and that I can get 10, 20, 30, and 40 over pistons. It was obvious I needed at least .020, but ended up with +.030.

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

Tom 75 is a standard bore stamping on the crown of the piston. Remember though that Hodaka did not make odd size piston kits for the 90's. They were Std, +.20 and +.40. Rocky prior to becoming Tucker Rocky did make +.30 sizes which might still be available.
I hope this helps
Thank you
Paul

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