Well after several weeks of crappy weather I had some time to fiddle with this darn engine some more. After running OK on the bench I put it back into the plane and headed for the field. First two flights went fine, engine ran real good. Fired it up the third time and it sounded bad (surging a bit). Tried to advance the throttle and it refused to accelerate. So I figured I'd open the low needle a little and it seemed OK on the ground, but after a few minutes in the air it was threatening to quit when I tried coming off idle. I figured I'd better quit flying it for the day.

Next I decided to mix up a gallon of petroleum based 2-stroke oil (pro-honda GN2). Headed back to the field. Started the engine at high idle and let it warm up good. Down to low idle, engine surging erratically and hesitating off idle. I guess the synth. oil wasn't the problem.

So today I went to the local small engine guru and talked for about an hour with him. He suggested that a leaky seal or worn gasket could could cause erratic fuel delivery. He said that he has located this problem before by spraying starting fluid around the seals with the engine running and if a seal is leaking some of the starting fluid will be drawn into the engine and you'll be able to hear the effects. So I tried that. No noticable difference. He also suggested that the spacer block between the carb. and cylinder could be warped and that you can compensate (for diagnosis mind you) by doubling up the gaskets on either side. So I punched out a fresh set and tried that with no success.

Before all this I tried the carb. mod. on the IMAA website and that didn't seem to help either.

I also thought that since the engine worked the other day for 2 flights, that the problem could be the ignition battery. I started that day with a freshly charged pack and thought that as the voltage went down maybe it was causing problems. So I charged the ign. battery and it didn't make any difference.

So what does one do at this point? I called and ordered a DA50 and will return this one to BME for a look. Hey, at least now I'll have an extra engine lying around (so what if it doesn't run).

Thanks to everyone for the suggestions and I'll let you know what I hear from BME.

Ben