Originally Posted by
1QwkSport2.5r
I tried running a tank of 15% through my S90K in the fall and it crackled like no tomorrow. I stopped at a couple ounces and went to 5% and the crackle went away. I just stick to 5% most of the time; it's a safe bet - at least where I live. At higher elevations, the extra nitro helps with the lack of oxygen in the thinner air. I'll have to remember to keep that in mind when I give advice.
I had same experience, along with blowing plugs, with my Como .90. Also same with ASP .91 and 1.08. I now use no more than 5% in most of my 2S engines.