Ignition Check

[pilotyoung]

Today I went to fly my Onex. I started it, warmed it up, and did the ignition check. When I turned off the secondary ignition, the rpm dropped 400 rpm, the engine ran rough, and if I left it on only the primary ignition for a few seconds, the egt's on cylinder 2 & 4 would drop to zero. So my opinion is that cylinders 2 & 4 are not firing.

I went back to the hangar and took the top cowling off and look at the installation instruction. It seems like a really simple system. I checked to make sure that when the ignition switch is on, that the ground was removed from the p lead terminal. I even took those two wires off the magnatrons and ran it again and same problem.

So it seems to me that the problem can only be (1) a bad magnatron, (2) bad spark plug wires, or (3) bad spark plugs. I don't think that two spark wires or two spark plugs would fail at the same time so this leads me to the magnatron.

Has anyone else experienced this problem? If so, what was the solution? Is there any way to check the magnatron?

Thanks in advance for your help.

[wlarson861]

I had a similar situation, but it was the electronic ignition that sputtered when I turned off the primary. Turned out the ignition wire had slipped down and rested on the exhaust pipe and melted through part of the outer shield. Replaced the wire and it was fine.

[pilotyoung]

Thanks for the response. It is clearly the primary on mine that is a problem.

[Onex107]

I had a similar failure and found that the magnatron that served those plugs had changed position and lost the .010 clearance and had rubbed on the fly wheel magnet smearing the laminations on the bottom of the coil. Replaced.

[pilotyoung]

When I was looking at the magnatron yesterday, it looked like the nuts on the forward side are hard to get to and if dropped would fall into the engine. Do you have any suggestions for insuring the nut and/or washer does not get dropped?

Thanks

[Scott Todd]

I've done that before. I stuffed a rag or paper towel on the front side of and over the gear to make sure they fall aft. Then I stuck a few magnets under it coming in from the side. I used some cheap ones from Harbor Freight that are on a little telescoping rod. I had them really close to the nut. I got one with pliers and one fell to the magnet. Be sure to have the safety measures in place when re-installing.

Scott

[pilotyoung]

Thanks those are good tips.