Hi Iluv,

I would say that your engine should be pretty well broken in. May I also suggest that you not follow the break-in method listed on the manual. It is kind of a throw back to ringed engines. You will want to break in an ABC engine on a somewhat rich two stroke, not super rich four stroking. This has to do with allowing the sleeve at the top to quickly heat up and expand. I would suggest that you back off on the nitro content down to 10%. The castor/synthetic oil blend is ideal (the best of both worlds) as far as in protecting your engine against a lean run. IMHO, OS is suggesting too large of a prop for the 55AX - the 55AX put out alot of power (like a .60 size) with the foot print of a .46 but it is still not a .60 size engine. How heavy is the Kaos ARF? Are you going for speed or thrust (unfortunately, you can't have both, just a compromise). I have a 55AX on a Hangar 9 P51 Mustang PTS that weighs alittle over seven pounds. I like to run my engines a little rich to make them last longer and the egnine has about 14 tanks of fuel through it. I originally started with a APC 12-7 on the engine. I ran 6 tanks through the engine on the bench and six tanks in the air with the 12-7. I was hitting around 10,000 rmps (running rich). I made a decision that if I wanted speed, I would either drop down to a APC 11-7 (12,000 rmps) or go with more thrust (vertical performance) with a APC 12-6 at 11,000 to 11,200 rmps (still a little rich). I went with the 12-6 and have two flights and I must say that I love this engine. I used to have an Evolution .46NT in the Mustang and it was a poor performer. The plane flys faster with more authority with the 55AX at half throttle compared to the .46 full throttle. With the 11-7, your Kaos should haul butt (unless the thicker airfoil is holding it back). If I can help anymore, let me know.

Happy flying!