I said earlier that I've run the C90 for ten years on Mogas with no trouble.
True it's never missed a beat, but I have replaced both rear cylinders due to exhaust valve serious wear during that time. Noticed by a lack of power slowly creeping up over months.
One of them I could see daylight between the guide and stem!
Is this mechanical wear caused by hard carbon build up on the stem/guide?
What are the bad effects of running full rich all the time?
All the plugs are black, no sign of the brown that I would prefer.