cj,
I'll paste some info on ABC engine break-in from another reply I gave. If your's isn't ABC or ABN, ignore it and find proper procedures.
Dennis-

ABC engines have an Aluminum piston in a Chrome plated Bronze sleeve (ABC), or Aluminum piston in a Nickel plated Bronze sleeve (ABN) which the OS's actually are.

Because of the different rates of expansion of the piston and sleeve, the sleeve is bored to a taper making the piston/sleeve fit "squeekey" tight at top dead center. (Sometimes they're so tight it's difficult to turn them over when cold.)

IF you run one of these "4 cycle" rich, the excess oil/fuel will not allow the engine to get to operating temperature, and the piston will rub against the sleeve causing excessive wear. The end result will be too little compression for a good, powerful engine.

Proper break in? Tune the engine until it's completely 2 cycling (at full throttle obviously) but not peaked, and run it for 3 to 4 minutes. Shut it down and allow it to cool enough to touch the cylinder head.

Restart the engine and repeat. Run through at least 2 to 3 tanks this way, then you can fly it. Do not lean the engine much beyond the break in setting until you've run a couple more tanks through it.

Of course, you never run an engine at "peak" RPM, always at least 300 - 400 below peak. (They lean more in the air when the prop unloads.)