Check the coil pack mount brackets first to see if any of them are now broken. Pull the air filters, probably clean them too, while you have them off and re oil, and inspect those funky "L" brackets that hold the coils in place.
If they are broken, the coils can rub on the engine mount and rub through and short out the coils windings. If they are broken, it's highly possible you have a vibration problem that caused them to fail. Balance the carbs, balance the prop, and verify the Clutch, Dogs, and Bellvue torque washers are in spec and not worn on the gearbox, causing vibration problems that break those brackets. On a Rotax 912ULS... not balancing causes a lot of failures of components, you have to stay on top of it and keep things in proper adjustment. The motor running a 11.0 :1 compression ratio is pretty violent if the engine RPMS are too low, making things speed up and slow down, lack of rpms creates lack of momentum, so speed things up a little bit.
Always have the owner idle the engine at somewhere very smooth running between 2000 and 2500 rpms on start up through warm up.
Always a good place to look, do a search on broken coil mounts here in the RV-12 section of VAF.
RV-12, #212 N72DJ, bought flying. A Blessing in disguise. Thank you Double D!
Last edited by NinerBikes : 12-17-2020 at 02:51 PM.