Decoherence, it actually sounds good except for the four stroking, then it falls on it's face. Nothing there... will not build revs... Someone said in another post, it's like it hit the rev limiter my 00 ford has at 93mph... just will NOT go past that! I dropped the needle to the top groove and tried it again this morn. nada... Now I'm gonna take the stock pipe off and see what's goin on in there. Oh, I didn't mention... my mab sounds quiet... quieter than I think it should sound. Seems like there is more exhaust noise coming from the front than where the pipe dumps on the ground. I do NOT want a loud MAB! (I'll be in hot water with the tax collector soon enough. Don't want to give them additional reasons.) It's all good. These lil thangs are ez, and fun to work on. rc btw msrfan had posted instructions to balance a motor crank... but I don't think he ever posted the final results... balancing quality components is the key to hi-rpm without vibration.