Run of my Fox .35

getback wrote:IT does sound good TD , I was wondering is the old flat style needle what causes it to keep wanting to go to 2 stroking or just the break in doing that ?

Ken Cook wrote:           I wouldn't worry about it going into a 2 stroke as it's not going to harm it in anyway even if it seizes. It will seize and all that's needed is to let it cool off and go at it again. The problem is when you continuously run it and let it seize. It's a binding condition that isn't going to go away. It won't break in because after the so called gallons of fuel everyone claims is needed to break these in eventually lands you a engine  that's worn out. I can take a brand new Fox and have it flying out of the box in less than 2 runs without overheating and seizing with a little massaging to the internals. Running them rich isn't going to insure a engine that's going to last a lifetime. It's very harmful to the rod especially a Fox rod which has no bushings in it. Due to the binding, the thin and weak larger end of the rod eggs out.  I myself personally drill oil holes in both ends of the rod. I do an extensive clean up of the inside placing a clean and polished radius on the mating side of the rod to the crank pin. Allowing it run a bit faster with little load is less harmful to the rod and liner than many think. The engine should be run in a fast four stroke blipping into a wet 2 stroke occasionally pinching the line and letting it run into a fast 2 stroke. A thin bladed Master Airscrew 9x6 is very good for breaking in the Fox. It get's it out of it's vibratory state and places a adequate load on the engine without letting it over rev. If the engine can hold a solid two stroke when the fuel level is almost depleted without overheating and sagging it's ready to come off of the bench. If it continuously sags and locks up it needs to be addressed and no amount of run time fixes it. It ruins it. Certain things need to be evaluated. Liner fit to case, crank fit to crankcase especially the radius along the face of the crank web and the back of the crank bushing itself. Many times the crankcase needs to be dressed along the front of the case where the prop washer seats on the crank. The piston liner fit down near the bottom end of the cylinder in and around the exhaust ports. I think Fox cut the porting into the cylinder using an axe. Any bind whatsoever or anywhere  will generate heat and resistance just compiling break in time and results.

I found the harder you run them, not only the better they run but the more reliable they become. I don't run them with the prescribed 29% oil and never had one fail as a result of not using high castor oil. I race them, fly combat with them, use them for sport, etc. They run better than perfect when run on Powermaster GMA 11/22 oil.

What I found to be more problematic to the engine is the use of high castor oil especially after lengthy run times due to the engine getting so varnished up the carbon feels almost like an engine that has rust within it. Just my findings. Ken