What specs are you looking for.

tkg was correct, it is a Fuji 50. The problem is I still can't find much info on Fuji's Web site about anything other than the newer engines. I was planning on contacting them for parts availability info.

I have a Mustang 50 in a Giant Aeromaster and it could use some rings. It's a strong motor, I turn a 20x8 Zinger Pro and she will fly vertical all day long. A strange problem has developed though. The motor now runs poorly when in level or decending flight (RPMs rise and fall in a cycle about once every 2 seconds) but runs perfectly in inverted flight. Seems to be a fuel delivery problem. I'm using a carb from a Zenoah G-62.

Are you running this in a Byron Mustang or another plane?

Jason