My first TT 120 had very poor compression, even after several tanks of fuel, running rich on the bench. Sent it back to Ace, the importer. They said it was ok. Ran it some more on the bench, put it in the airplane (25% Edge 540), and had very erratic results with it. Added a Perry P-30 pump, with which I am familiar. Didn't help much. I finally yanked it out and sent it to Frank Bowman in New Mexico. Frank put a new ring in it, and said the initial ring was far from round, was polished from running only in a few spots. I broke in the new ring, and the engine runs great.

I bought a second TT 120 and put it in a Goldberg Sukhoi. This engine had good compression from the beginning, and pulls like a moose.

It sounds to me like you got another poor ring from TT, or else the ring is worn out. Good luck in getting it fixed.

Clair