Intermittent ignition problem

[billmaxmcw]

I built and fly a 2012 Aerovee Sonex. Recently, one cylinder began misfiring when on magnetron only. And only after being in the air a few minutes, not on initial warmup. No better after spark plug replacement. Any ideas?
Bill

[mike.smith]

Bad mag? Bad mag spark plug wire (cracked insulation or melted through (touching exhaust))?

[robin]

I have the same issue on one plug #3 cylinder but on the secondary (coil) ignition system. I have replaced / swapped every component of the secondary ignition system (from trigger to plug) so I am almost certain it is not an ignition system problem. It occurs above 2500rpm but is just noticeable very intermittently at around 2000rpm and steadily increases to a steady miss above 2500rpm. The timing appears to be pretty good as swapping between systems below 2000rpm shows no change in rpm. I have been adjusting the mixture and making sure the valves are correctly set but so far no solution.

Sorry I can't give you a solution but if this is happening to 2 of us it has most likely happened to others so hopefully someone can tell us how they fixed it.

Robin.