Jens,

Thank you for taking the time to copy the book pages for me. Because of the time difference between us I was able to read them before going to the field today. I did not find anything in the pages that was in conflict with my practice, but I have gotten into a habit of just starting and flying, and haven't touched the compression setting in a long time. So it was good to have a reminder to take time and check settings and performance.

My OS .40 conversion starts very easily. I turn out the needle 1/2 turn, choke the carb for one turn of the prop and then apply the starter. The engine usually starts immediately as it did today. I let it warm up until the engine note is smooth and then I turn in the needle for best running and then back a little to account for the prop unloading in the air. The compression is, I think, just about perfect. If I lean out too much I begin to get that crackling note in the exhaust. Turning in the compression makes the exhaust sound go flat and the engine speed begin to drop. If I reduce compression from its current setting, the engine does not throttle as well (it is normally very responsive and does not load up when going from low speed to high speed). Flight performance at my settings is very good. The plane is relatively heavy and sized for a larger engine...yet I get short take-off distance and impressive vertical performance. The needle valve setting today was 1 1/4 turns out, running on muffler pressure. Fuel economy is very good, and, there is no smoke other than a faint white fog at full throttle. Immediately after a run, the muffler is cool enough that I can touch it briefly without burning my fingers.

Your comments have made me think about my mix. I have been running about 23% oil (50 wt automotive). I am wondering if more oil would help to keep things clean. I notice that Slope-soarer's mix has heavy oil and yet his engines seem to run quite well. I was inclined to think the oil might be a problem. . .but your comments make me wonder if I simply don't have enough of it. Since I am running fairly high ether (over 30%) I can try to reduce it down to 15% and increase the oil. That way I won't have to give up any of the energy from the kerosene. I could use my current mix as a venturi prime, since the engine seems to start so well on it.

Thanks for your comments.

George