2002 Yamaha YFM660 Grizzly factory service and repair manual, Page 355Get this manual
IGNITION SYSTEM Spark plug gap: 0.80.9 mm (0.030.04 in) CORRECT INCORRECT
Repair or replace the spark plug4.Ignition spark gap
Disconnect the spark plug cap from the spark plugConnect the dynamic spark tester as shown
2 Spark plug cap Spark plug
Turn the main switch to "ON"Check the ignition spark gapCrank the engine by pushing the starter switch, and increase the spark gap until misfiring occursMinimum spark gap: 6.0 mm (0.24 in) OUT OF SPECIFICATION OR NO SPARK