Went flying last weekend. On first startup it ran fantastic. After about 8 minutes of flying it started to miss. Brought it in for a landing and nothing else I could try would make a difference. Moved the timing back and forth, fiddled with the needles. I did notice that my crankshaft had a little play in it and that the magnet had struck the sensor. So I figure the crankcase or bearings were bad. I had several more engines at home so I just decided to build another engine. When I pulled the engine out, I found that the ignition wire to the sensor had rubbed on my engine mount and was shorting out. So I think I have found my problem. Anyway, Since I had several crankcases, I went ahead and rebuilt the motor using the same head and piston with same carb and muffler. I did find that the crankcase I used this time had wider transfer port openings. After all put back together, this engine seems to have more compression. And no slack in the crankshaft.

I was really excited on my first flight cause the engine was running really well. I rerouted the ignition wire to the sensor and put some conduit around it to protect it. Hope to run it this weekend.

This does explain why the engine sounded so much like it was out of time.


Jim