Mag Checks

[ChiMike]

A first for me today. 914 mag check had an issue after an oil change. Oil temps and pressure in the green. 3200 rpm, right side key—good, left side intermittent rough. Rpm’s within 150 of right side.

I finished the check and shut down: my mechanic was there and asked if I’d felt-seen it. Yes. I did another start/run up and mag check, this time if it was there it didn’t seem as severe.

I needed to wash the plane—finished that, and did a taxi lane drive checking out all my actuators and flaps, etc., as well as drying down the wheels, rotors and brake pads through movement. At the end, oil temps and pressure in the green, I did another run up and mag check at 3850 rpms. The roughness returned left side key only but still within 150 rpms of the right side only values. At ‘both’, varying engine rpms, everything feels and sounds fine.

Any ideas?

[cole505]

Hi Mike,

I think maybe some wiring got wet causing  a grounding issue......... once the airplane was hot and dried out did it still continue.....

Ray And Lucy ✅😎✈️👍🏻🇺🇸😊😊

[LSA Flyer]

Sounds like a single spark plug is not firing. Give each plug wire attachment boot a firm pull to see if one is loose. Could also just be one fouled, but that's uncommon with Rotax. If that doesn't solve the misfire I'd pull all the plugs and check the gaps.