Have had similar vibration problems, although on a test stand. This thing is a real shaker compared to the OS 2-strokes I've typically run. This is my first 4-stroke and I, for one, am not sold on 4 cycle engines yet. Really touchy LS needle valve to say the least. My Saito 100 was mounted to a test stand and run according to the break-in instructions. Prop was APC 14x8 and fuel was Wildcat YS 20/20. Valves were set at .0004 prior to initial startup. The break-in went rather well except for the noted vibration that I considered excessive. After about an hour, the engine would idle at 2100-2200 rpm and top out at about 8800-9000 rpm. Final HS needle valve setting was 2 1/4 turns out.

After 90 minutes total run time mounted upright, I checked the valves and found that they had opened up considerably. I reset them to .0004 and inverted the engine because that's the way it's going to be mounted in my H9 60 size P51 Mustang. Wow . . whole new ball game. HS needle valve had to be opened an additional 1/4 turn and the LS needle valve had to be leaned slightly. Again it seems to have a good steady idle of 2100-2200 rpm and about the same top end. When left to idle for an extended period, the engine will die after 45 seconds. Yea, I've done my reading, but can't seem to come up with a cure for this. Other than that, throttle response is excellent in every way. When in the plane, the fuel lines will be considerably shorter than on the test stand which should help (I hope). Click on the link below to see it running inverted.

http://s88.photobucket.com/albums/k1...t=100_1246.flv