Probably a silly question, but how do I tell when my 35 is broken in?  It has had about 2 quarts of Superfuel through it, the last one flying in a rich 4 stroke.  The engine runs got better yesterday as the flights progressed.  I'm afraid to lean it out too much - it's running so rich that it won't break in maneuvers, but it's lots more fun than watching it on a stand.  It runs out a 3 ounce tank just fine and doesn't seem to be overly hot at the end. 

I would think that if you aren't having tank problems i.e. going lean, cutting out, etc. then it is safe to start leaning it out a bit. You indicate that you are using Superfuel so with all that oil it should be OK.

Some folks have reported one lean run ruined their Fox .35. That hasn't been my experience. They seem to be pretty bullet proof if you run lots of Castor. One of the best Fox .35 I had was abused by me when I was young and when I bolted it on a Ruffy in '65 it was a winner... so maybe it was the luck of the draw.

I have heard the statement many times that Fox engines have burned out on a lean run. I have never had this happen. Even when I ran my .29R "Bathtub at a lean run with 40% nitro and a 7/10 Top Flite prop it was a happy engine. Given enough oil there should never be a problem. As stated if you are not experiencing any major problems ie cutouts engine going lean etc., it safe to start leaning it out.

Bill Gruby

PS-----I am in no way saying that fried engines don't happen, I've just been lucky I guess.