Back before I knew any better, I'd follow the "instructions" for 2 cycle breakin myself. I broke a particular engine in sloppy rich--with plenty of castor. Didn't want to hurt it. I ran somewhere between 1/4 and 1/2 gallon of fuel through it on the ground. About the second flight in the air (again, still rich, but not as rich), the bottom of the conrod shattered. I definitely believe that the conrod was damaged and weakened during breakin because the cylinder wasn't getting hot enough to expand properly. The constant high compression strokes at 7000 RPM's during breakin was too much for the conrod. These engines need to get hot during breaking. The idea of rich is for lubrication, not for cooling. If you keep the cylinder head too cool during breakin, you are asking for trouble. JMO. I have since broken in (ballpark figure) 12 to 15 engines--including mine and others--and have not had one single failure. I also have never broken in an engine that rich again.