ORIGINAL: mswify
Thanks guys for all your help, I don't have a filter so this may be the reason, and about the 5% nitro fuel the engine was doing great with it at first before it started to lose power, I think I'll also change the prop. its a 13x8 size may be I need a smaller one.
Ok. Changing the prop to a 13x6 is a good idea as that is about as big as I can go on my Saito .72 without lugging it down and overheating it. By your own admission you have stated that you don't have enough experience with engines so is it possible to get an experienced modeler to help you?? Also, please heed the opinions of the experienced people on this forum who have suggested to "CHECK THE VALVE CLEARANCES". It's not a difficult thing to do but it is necessary to do at least once after breaking in the engine. I'm sure that is stated in your owners manual. Obviously something has changed for the engine to go from running great to barely running in the same plane. Valve clearances, bad fuel, high end needle valve way out of adjustment or using the wrong plug are the usual reasons.