Jim, I own the Ap.09. I like yourself, want to build a plane for this engine. I was thinking Akromaster as well. The engine I have is running 18 k+ on the bench with a 7x4. It runs terrifically and starts equally as well. Another fellow on here was asking recently about the Ap .09. With this kind of power I believe it would suit this plane well. The one drawback I see is the rear exhaust. The engine comes with a muffler that does turn down the exhaust but it knocks off considerable rpm's. I believe it was almost 3k. The engine does weigh a bit but the current Akromaster I'm flying is using an Enya.15. The Enya is heavier in which the plane needed 3/4 oz of tailweight even with a tongue muffler. If I elected to go with this engine, I'd lose the muffler which would put the tank directly into the exhaust heat which I feel wouldn't be good. The Akro has a real short nose which already limits you too tank choices. I thought about mounting a tank inboard to counteract this problem. My Ap is quite an engine in my opinion. It has ABC piston sleeve, ball bearing supported crank, and additional features like o-ring sealed back plate. They do make a venturi set up for control line use which I might purchase. The carb can be simply wired open. From an r/c standpoint , it idles beautifully and responds to full throttle blips quite nicely. I like the fact I can run different levels of nitro in it up to 35%. I purchased mine used which made the price even more entertaining. I think its a well built engine for the price but I've never flown it on a plane to date. From what I've witnessed on the bench it seems like a winner. Compared to the competition, I don't think there is another .09 making the same power. I also own a TD .09 which likes to run one way which is flat out. The TD .09's are getting a bit harder to find the stock plugs which also makes the Ap a plus to own. I'm sure an adapter would be the alternative to the TD its just another expense though. I've found these to drop performance a bit though. Its weight is a big plus factor though. It seems like a lot of engineering went into the Ap for its size. If you decide to use this engine, keep us posted. Ken

Jim,

If it's anything like my AP Wasp, it will be filthy inside!

Do not start it, or even turn the engine over by hand until you take the back cover off, and wash out the crankcase with a good solvent. Kerosene, Acetone, etc. Even old model fuel would be better than nothing.

Better yet, if you can disassemble the engine, and run everything through a solvent bath.

I wouldn't take the carb off the case, but be sure to remove the needle valve, and flush out the spray bar by blowing solvent through the fuel inlet with a squeeze bulb, or syringe. Wear safety glasses!!!!

Evidently the AP factory is in a building with a dirt floor. 

My engine has very nice castings, and machine work, but the case was full of crap that shouldn't be there.

Bill

For now I'm getting an ap .09 for $46 and try it on the sig acromaster.