depends what your problem is... the thing with the nitro engines, they are carbureted so they are a bit sensitive to tuning... they also need to be adjusted and readjusted with the weather, factors like air temperature and humidity affect the engine's performance because the amount of oxygen that gets into the engine changes as the air density changes, etc. etc. etc... i think it is usually easier to get to run rich to get it started and then adjust your needles as need to get to run right... usually the optimum is so that it is running stong, not too lean, there should still be white/blue smoke coming out of the exhaust even at wide open throttle... that insures that your engine is still being getting the proper lubrications from the fuel mixture... that's also important for keeping your engine alive, it keeps the temp. in the optimal range and keeps your engine compotents from wearing prematurely....

i don't know what symptoms you are getting when you are trying to start it up, if it just won't start, or kind of burn the fuel but it's not enough to get it running or if it will start but when you hit the gas it bogs down and dies... give more details...