sintoms> the engine starts at idle but when i open the trottle it stops ,( no is not lean)tryed to open or close the needle, cleaned the carb ,no result at all.Then I cheched te plug it look PERFECT(i refer to the shape of the coil)the plug is a R 2 that worked good on my os 1.60.I tryed to change the plug with an os 5 the engine is now running good. I can not understan why a plug that look good can give so much troubles.When i had these prob I was using cool power 15% instead 0% nitro and 18% aerosave can a change in oil/nitro be the explication?