The Hodaka Club Forum

I received my new cylinder, piston and ring for my Super Rat 93b project. The cylinder is new standard bore. I checked the piston to cylinder wall and it is good as near as I can tell using feeler gauge. When I check the ring gap of the new ring I get .013”. My understanding is it should be .004 per inch of bore which would be .008”
Is .013” acceptable?
Thanks.

I always start with, "If it was mine". Common happening. The gap will quickly get wider as it breaks in. I'd run the one you have for a while and then replace it with the next oversize and file to fit. Ok as is but you do lose a tiny bit of compression. On my short tracker of yesteryear the ring was replaced after each racing event to start with .008 gap. Maxie

Thanks Maxie,
The NOS cylinder I bought was one that had some water damage and was honed to clean it up. I suspect this is why the gap is on the big side. I do not have a good bore gauge to confirm this though. The bike will not be raced, at least as long as I own it.
Bob

One thought might be to order a set of .010 rings and then file them down enough to give you the ring gap you need/want. I believe I’ve heard that mentioned here before. Victor

Information by wiseco on the web for TWO STROKE engines indicates a ring gap of .010 to .014 would be about right for a 2" piston.

Pictures shown in this article display a water cooled single cylinder unit.

Since heat expansion is the reason for the ring gap it seems that an air cooled might be better served by the larger gap indicated.

Wiseco talks about gap filing, but not about going to the next size ring and filing down to "spec".

A too small ring gap could be catastrophic. Too big could be a performance worry, but I'd run what you've got at .013.

A compression test is probably what you will want to answer any concerns.

I think you're fine with what you've got.