I recommend the NGK R6725-11.5 spark plug for 100% duty cycle operation.  Gapped at .010" to .012".

 

Race car settings.       There you go...............rotary talk.

 

Lynn E. Hanover

 

This is what I would do.

 

Get all of your tuning done on the ground and or, just above a long runway. Install a heated oxygen sensor,

 

Plug heat ranges in the 10s are for heavy street use. Not used (or should not be used, my opinion) for a 100% duty cycle as in aircraft.

 

 If 10s cured your problem you have already demonstrated to yourself the problems of a too hot a (high heat range) plug. Once the tip of the plug is overheated you have lost control of your ignition timing. This is a very bad idea. Followed by preignition and or, detonation.

 

Both can lead to severe engine damage.  Once your testing is complete and long flights are next, I would remove and discard the stationary gears and magnaflux the rotor gears. You can check all of the engine parts at that time.  

 

The NGK R6725-11.5 plug is gifted to most competitive race teams by Mazda.

 

Know what your timing actually is. Mark your flywheel teeth with colored paint. Easy to see and very accurate.

 

Lynn E. Hanover