Break-in

Face it, everyone has their own way to break in a nitro engine, so I'm not going to try to tell you "the" way it "should" be done. It is generally agreed that you should not use much throttle during break-in, and recently it has become widely known that you should not just let it idle, but bring it up to temperature and let it cool alternately, for the best results. Anything more specific than that, and opinions diverge.

I had to break my truck in the evening before I promised to start racing it. Another race event was going on during this time, so I could not turn on my radio and drive the truck around. The Kyosho engine started immediately once I primed it by plugging the exhaust with my finger and giving the pull start a few tugs. I set the idle to the point where the clutch was trying to just barely engage, and let it sit on the bench, for the first tank. I was using Traxxas 20% "Top Fuel," known for good oil content. The engine barely got warm. I let it use up the tank and stall out on its own.

For the next tank, I leaned out the needle valve 1/4 turn at a time, blipping the throttle very lightly with the tires dangling free, until I got some temperature buildup. I did not have a temperature gauge, so I used the "spit test" (drop of water-like substance transferred from the finger to the engine head) to make sure I wasn't going much over 200 degrees F. For the "spit test" to be effective, you need to do it close to the top of the engine block. Temperatures at the top of the head will be much lower than the temp of the piston & sleeve and block. At the end of the tank, I let the engine cool almost completely.

I went through five tanks of bench break-in, giving watching the temperature and adjusting the high-speed needle as needed, keeping a close monitor on the temperature of the engine. Every few minutes I would pick up the truck and clear it out, giving it up to 1/2 throttle.

On tank six, it was race day and I was able to take the truck out on the track and run it. I went really easy on the throttle. Not until the seventh tank did I start opening up the throttle.