Hi Dave
A new needle fixed the problem of getting a clean adjustment. I've flown the engine 3 times now with the ultrathrust and have excellent power, idle, throttle responce etc etc.
But I have an anomolie. The engine with the OS muffler behaved like any normal engine on this plane. I set the max rpm about 300 below peak and the idle a little rich to counter a tendency to run lean at the mid range. Everything worked fine.
With the ultrathrust the engine is going very rich in the air at full throttle. I first set the ground rpm at 11100, peak is 11600. In the air it got very rich at full throttle and would hold the rich setting thru big loops and long verticle up lines. it would come off the rich setting slowly on outside loops. I ran the first tank out with no change. I set the ground rpm to 11300 and tried again. No change except it was a little less rich in the air. I set the ground rpm to 11600 (peak) and tried again. Still the same except it will now clean up on long uplines and outside loops but it's still rich while flying straight and level at full throttle.
Is it possible that this is something peculiar to the ultrathrust? I'm a little reluctant to lean it further. I have found I can turn the needle another 1/4 turn in without further change to the rpm and before it starts to sound lean. I have had similar experience with a straight pipe and the fix was just to lean em out a little more even though they seemed at peak. They would cool in the air then go rich I guess.
Any short quick thoughts.
Denis