I purchased a new BME 44 w/CH Syncro Spark ignition second hand (never been run) and installed it on my Midwest CAP. I fired it up for the first time on some 32:1 Lawn Boy Ashless and ran a tank of gas through it on the ground. Filled it up again and flew it around at half throttle or less. After about 10 minutes of flying it started to run very strange at half throttle or just above and landed thinking it could be a fuel low level issue.

Filled up the tank, charged all the batteries and ran the plane on the ground and it ran fine at half throttle or below. As soon as you bring it up past half throttle the RPM varies rapidly at a high rate (steady rate of couple of times a second large RPM flux). Changing the high and low needles had very little effect. I thought that the ignition was the most likely suspect so I called CH and they suggested I send in the motor.

I sent the motor in and got it back less than two weeks later with a note that they changed a part in the ignition and ran the motor and adjusted the needles. I was very excited that the problem was solved. Yesterday I installed the motor and to my horror I had the same problem upon running up the engine. Fuel tank and Batteries were the only thing left I could think of that may be causing the problem. I put together a brand new Dubro tank and connected it to the engine and the problem persists. I tried a different 1400 JR pack directly attached to the ignition and the problem persists.

How can this be? If it were a carb problem CH would have noted it when they bench ran it, assuming they bench ran it. I believe they did as the spark plug and clamp were missing when the engine was returned to me. I also tried a different plug and still am having the problem.

The easiest thing I can think of the determine whether or not it is an ignition problem is to stick someone elses ignition in it. Unfortunately none of our club members have one lying around and I don't want to ask them to pull one out of their plane. Any suggestions?

Thanks for your opinions!