If the engine is new, there should be break-in instructions in the manual. If there aren't, just run about 2 tankfulls of fuel through it with a very rich setting. In case you're not familiar with that term, it means to open the needle valve enough that you see a fine spray of fuel leaving the muffler. It will be running pretty sloppy, but it will be getting some well needed lubrication.

After that turn the needle valve in till the engine peaks, then back it out until you hear a noticeable decrease in RPM. You can now get your next 3 or 4 flights in while the engine is running like this. After that, tweak it again to peak, then back it off just enough till there is a very slight (Almost unnoticeable) decrease in RPM. Your engine is ready to go.

As for balance, the instructions or plans should specify where the plane should balance. This is called the Center of Gravity or "CG". So if they say "three and one half inches behind the Leading Edge of the wing", put a mark on the bottom of the wing, (or side of the fuse below the wing) and with the plane ready to fly (I.E. engine radio, covering but NO FUEL) Lift the plane with one finger on either side at the marks. It should sit level, or SLIGHTLY nose down, but not tail down!

If it doesn't balance properly, move the battery pack forward or back until you get it as good as you can. If it still needs more, add some weight (Lead fishing weights, buckshot etc) to the nose or tail until it's right. (Also make SURE the weight can't come loose! engine vibration is a lot stronger than you think)

IF you have any other Q's check out this article:

http://www.rcuniverse.com/magazine/a...?article_id=84