This may be a dumb response but have you tried diffrent fuel, it could be bad. I built a skybolt arf and during the build I bought a new jug of fuel and used it the first time I flew it. I had engine trouble from day one. It was a Saito .91 from another plane and I knew it ran perfect. The fuel was getting worse each time I flew but, it was a new jug so I never thought fuel I kept trying to adjust the engine. One day it would not run at all so I had brought another plane and I fueled it up. That engine did the same thing (BINGO) I found the problem. I happened to have bought a new jug that morning and I put that in the second plane and it ran fine. I fueled up the skybolt and it's been running fine ever since.