Yamaha 20C Owner's Manual

Also see for 20C: Service manual Owner's manual

4-11Before fitting the spark plug, measure theelectrode gap with a wire thicknessgauge; adjust the gap to specification ifnecessary.When fitting the plug, always clean thegasket surface and use a new gasket.Wipe off any dirt from the threads andscrew in the spark plug to the correcttorque.NOTE:If a torque-wrench is not available whenyou are fitting a spark plug, a good esti-mate of the correct torque is 1/4 to 1/2 aturn past finger-tight. Have the spark plugadjusted to the correct torque as soon aspossible with a torque-wrench.1 Spark plug gap2 Spark plug I.D. mark (NGK)GBSpark plug gap:Refer to “SPECIFICATIONS”, page 4-1.Initial of spark plug Plug wrench sizeI.D. markB 21 mm (13/16 in.)C/BK 16 mm (5/8 in.)D 18.3 mm (23/32 in.)903022qwSpark plug torque:Refer to “SPECIFICATIONS”, page 4-1.