I tried running some 100 Octane race gas in my R this weekend. I put MAYBE 1/3 of a tankful of it in, mixed with 2/3 premium gas (93 octane). My R is stock aside from the HRC kit.

After riding for maybe 15 minutes, and driving the quads to another pit (engine completely cold), it took me almost 50 kicks to get my R started! Once running, it ran fine, although there seemed to be a slight bog with the race gas. Anyways, with the engine hot, the quad fired up with one kick. Then, we drove home. At home (engine cold again), I could NOT start the quad. Me and my friend kicked it like 75 times, no start. I tried with choke (starter enrichment) and with hot start (leans) go, not even close. With the tank now less than half full, I topped off the tank with 93 octane, to dilute the race gas. I noticed the exhaust pipe reaked of the race gas...which is green and smells by the way.

I took the plug out, and it was wet, and maybe a little dark, but not black. I dried the plug off, and cleaned the contacts a little with a piece of paper, and used compressed air to 'dry out' the combustion chamber. Put the plug back in, and it started after about 10 kicks. Let it idle, ran it for a while, shut it off and it started right back up.

Today, it started after 2 kicks, and the exhaust no longer reeks of that smell.

Was the race gas causing me to be too rich? Did it foul the plug, making cold starts extremely difficult? Is cleaning the plug good enough, or should I replace it? Is the 10.5:1 compression too low for this mix of race gas?

Just wondering why the race gas did this. Tx.