A mistake a lot of new R/C flyers make is they run their mixtures too rich. You want to lean it out until you get peak rpm and can throttle up/down the full throw of the carb without having the engine burp. During break in for new engines, I run mine rich at max power on a test stand (vice) with a little servo mounted on the workbench to keep the throttle full open. I just leave it until about a gallon of fuel has been run through then I bolt it onto the airplane. I run the engines lean because you can go from a low rpm to a high without running as much risk of flooding the glowplug. Also, while holding the airplane, a preflight runup should include a few seconds at max power in level, nose down and nose up attitudes with you holding the airplane in the attitudes. This will help you isolate where/why the engine is running rough.