2006-2009 Honda TRX680 (TRX 680 FA-FGA) Factory Service Manual, Page 207Get this manual
CYLINDER HEADIVALVECAMSHAFT
TROUBLESHOOTING
Engine top-end problems usually affect engine performanceThese can be diagnosed by compression test, or bytracing top-end noise with sounding rod or stethoscope If the performance is poor at low speeds, check for white smoke in the crankcase breather hoseIf the hose is smoky, check for seized piston ring (page 10-2)
Compression too low, hard starting or poor performance at low speed
Valves:Incorrect valve adjustmentBurned or bent valveIncorrect valve timing
- Broken valve spring