Tom:

The advice above is great for a conventional two stroke with a conventional ring in a conventional steel cylinder sleeve.

The K&B "Ringed 40" does not have either a conventional ring or a conventional steel cylinder sleeve. It has a Dykes type ring in a chromed liner. The Dykes ring will not have any wall pressure to speak of run at a low power setting, and will take an inordinately long time to run in if done this way.

Put a 10x6 prop on it, start it and let it warm, then go to full throttle and peak the HS needle, then back it out to about a 300-400 rpm drop. Bring the throttle back to 1/3 to 1/2 for a moment, then go to full throttle again. When the engine reaches its maximum rpm back the throttle down again. Keep running the rpm up and down for the first five minutes or so, then go to full throttle and hold it. If the rpm sags repeat the high-low throttle for another five minutes and recheck the high speed. When it will hold high speed without sagging it's ready to fly, and be adjusted normally.

"Heresy!" I hear someone cry. Not so. The K&B 40 is a very special engine, I don't know of any other with the same construction. There are others with Dykes rings, other engines with rings running in chromed sleeves, the K&B 40 is an animal unto itself.

I have more than a dozen of the 40s, this method has given me excellent results and totally reliable engines.

Bill.

PS: The K&B 61s are NOT Dykes ringed, run them in normally. wr.