JAKA, I set the needles by a tach and the pinch test. Although some very experienced tuners might be able to tell 300 rpm from 400 rpm, I am not one of them. I can find the peak and then back off a few clicks but without a tach, I don't really know how many rpms I backed off, just that I backed it off and it is a little richer. So that is why I use a tach because maybe 300 rpm rich of peak is still a little lean in the air but 400 rpm off peak is just right in the air. When I am at idle or midrange, I use the pinch test. I like to get a little rpm increase before the engine starts to die. The tach comes in handy here too if the needle is set close to peak at that throttle range, because sometimes for me it is hard to hear the quick rpm increase before it dies. In the case of this engine, the pinch test at midrange didn't allow for much if any rpm increase, and the fact that there was no oil vapor out of the exhaust made me question if midrange was too lean. Like I said previously, the engine transitions from idle to full throttle without hesitation but seams to be right on the edge of being lean.

I don't use the oil vapor to tune the engine, just as an indicator as to the state of the engine. I know that with a vapor trail, most of the time it is rich enough. For most engines, you can run on the rich side all day but one run on the lean side might ruin the engine.

I flew the plane the other day and noticed that after a 6 minute flight of good throttle transitioning, I landed, taxied back to the end of the runway and proceeded another take off. When I went to full throttle, the engine cut out, (not blubber, just almost died) and then raced to full throttle. I aborted the take off and taxied back to where I was standing. I held the tail and tried it agian and there was no hesitation, so I attempeted another take off and the hesitaion happened again. I took off and came around for another landing and held the tail again and there was no hesitation. Upon running down the runway again I got the hesitation. This did not happen with a full tank of fuel. I think it might be a little too lean at midrange. My thoughts are that the fuel rushing to the back of the tank causes a momentary lean condition and the engine in mid throttle is already on the edge of lean, so as the engine throttle is pushed to full throttle, the engine goes lean but as soon as the throttle hits full throttle, the engine then is set rich enough to pick up rpms and resume running.