I have gained so much by the information on this forum. Now it is my turn to share a problem and a solution.
One of my planes is handicapped configured and goes to Purdue University each summer for a handicapped training program they have. I received a call saying that they were having trouble with the ignition switch. When going to mag 2 the engine would shut off. I shipped a new switch over night to them. The told me the old switch started working again and they did not replace the old one.
A couple of weeks later when the plane came back to me, they said they had no problems and returned the new switch. We began flying the plane here and for about a month there were no problems.
Then last Friday came. Finally a weekend of perfect weather was forecast and the schedule was full for both days. Student and instructor ready to go for a flight. Everything normal until mag check. When checking mag #2 the engine quits. Repeated tries and same results. They put the plane away and take a different one. All warmed up and ready to go when it is time to do the mag check. Same problem, engine quits on mag #2. No flying for these two plane. That meant no Saturday, Sunday or Monday. Mechanics around here don't work the weekends.
A weekend of research and a conversation with Rotax and it was decide that the problem may be in the SMD-electronic module. In both planes at the same time?
Well that is what the problem was. Easy fix because it was the top one on both. Odds were staggering for this to occur to two planes at the same time. I thought I would have better odds at winning the 748 million Powerball. Lost there too.
A few subtle clues that may or may not be related. On occasion we would detect a 100-200 change in rpm both on the ground and in the air. Could not duplicate at will and it never presented a problem as it would not persist. Not sure if this was the modules or not. Something we will be keeping an eye on.