1999-2002 TRX400EX Fourtrax Service Manual, Page 234Get this manual
IGNITION SYSTEM
IGNITION TIMING
If the engine must be running to do some work, make sure the area is well ventilatedNever run the engine in closed area The exhaust contains poisonous carbon monoxide gas that may cause loss of consciousness and lead to deathRun the engine in an open area or with an exhaust evacuation system in an enclosedarea
Start the engine and warm it up operating temperatureStopthe engine and remove the timing hole capConnect the ti mi ng lig ht and tachometerNOTE: Read the instructions for timing light and tachometer operationStart the engine, let it idle and check the ignition timingThe ignition timing is correct if the "F" mark on the flywheel aligns with the index notch in the left crankcase cover at idleIncrease the engine speed and make sure the "F" mark begins to move counterclockwiseCoat new O-ring with grease and install it onto the timing hole capInstall and tighten the timing hole cap