The 660 engine is a bullet proof engine. It's built for reliability, you feel it every time you use the throttle 😉 the lack of power but also the thousands of miles to go. I've seen the engine been manhandled in such ways that you can't believe without any visible damages. If it's a little lean don't worry it's only more heat and the cooling should work great. The low compression ratio should save it from any knocking.

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XTX 2011. Yamaha Hand Guards, Akrapovic slipon mufflers, Snorkel removed, Airbox drilled, AIS Blocked, PCV, Dynojet Autotune, Kev O2 Controller, Dna Stage 2, KN air filter, mini indicators, steel sprocket cover, cnc levers, cnc mirrors.