Proper break in?

AlphaCrow

About.com: http://www.mototuneusa.com/break_in_secrets.htm

What's the consensus on this? Sounds a little exaggerated, but I'm no mechanic. Keep expecting him to try to sell me something, the way he types.

shovelstrokeed

Well, he is not dead wrong.

The wear-in, I don't want anything breaking, should be a process of gradually increasing loads/duration of load leading to complete seating of the rings and a light polishing of other metal surfaces such as cam to lifter/follower interface.

Initially, say the first 10=20 minutes of running, I would just have the engine at high idle to allow the cam surfaces (the highest pressure points in the motor) a bit of time to seat. No loading required there, just time.

After that, pretty much what he says, cycles of increased load and increased duration of load leading to full throttle/max RPM. In truth, I would tend to spread it over a longer period than just 3 runs of each. Say 200-300 miles. The deceleration cycles are nearly as important as the acceleration ones.

On my drag race engines, I pretty much just use a 600 grit hone on the bores, put a little dab of cam lube on the thrust faces of the pistons and start the motor up with the walls and rings dry. By the time the cams have been through their wear in, the rings are seated or one good pass away from seated. Do keep in mind that these engines are torn down on a regular basis and the rings replaced after about 20 miles, so this wouldn't be a good strategy for the street.

OZDave

Also his "Heat cycles" theory is full of shit.

"The term "heat cycle" comes from the idea that the new engine components are being "heat treated" as the engine is run in."

The engine parts are not thought to be heat treated. Heat cycles refers to the minute distortion that occurs in engine components when the engine is changed from ambient temperature to running temperature. "Running in" an engine involves polishing the 'high' points of these distortions as well as bedding rings (and other things).
Interesting point that shovelstrokeed raised about cams. Some engines produce 200,000psi of pressure between the cam and followers. It is easily the most stressed part of any engine, and is quickly stuffed by letting a new engine idle for long.

In a nut shell, if you are racing the bike and rebuilding it every couple of races, fine, otherwise I think it is a load of crap.

Feel free to disagree.

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