Spark Plugs

Choose the correct spark plug for your engine and for the use of the engine. Manufacturers recommend different grades of plugs per engine. A medium grade plug (B7ES) is good for general use around town, dual carriageway or motorway. A cold plug (B8ES) will be required for motorway touring. 

Running an engine on a hot plug, flat out on a motorway would soon pink and overheat. Running an engine around town on a cold racing plug would cause misfires due to fouling up.

There are various plug types available i.e. NGK (personal favorite) or Champion for general use and Nippon Denso for racing. 

Grade NGK Nippon Denso Champion Bike Type  Use
Hot B7ES W22 N5 Standard Town
  B8ES W24 N4 TS1/tuned Motorway
  B9ES W27 N3 TS1/tuned Motorway Touring
Cold B10ES W31 N2 TS1/tuned Racing


Spark plug gaps range from 0.35mm - 0.55mm (0.016" to 0.022"), 018" - 020" is normally used.

Magneto type Inches Metric
4 pole  0.020 - 0.024  0.5 - 0.6 mm
6 pole  0.020 - 0.024  0.45 - 0.5 mm