Plug Types

BTH Components Ltd.

We have had good results with NGK plugs and some suggested types for popular machines are listed below. The NGK plugs have a good heat range so the suggested grade will usually perform well for most normal riding. If you have a modified motor or you are competition riding the suggested type can be a good starting point to find the best grade of plug. Use the gap recommended in your machines handbook. If you don't know the recommended gap, 0.020" (0.5 mm) is a good starting point. A plug gap of 0.0180"-0.020"was recommended for most bikes that originally used a magneto A large gap is not necessary unless you have plug fouling problems and just works the ignition system harder than necessary.

N.B. A local dyno expert who has tuned many race winning vintage machines has found that a plug gap as low as 0.007" (seven thousandths of an inch) does not reduce the power output registered on the dynamometer.

BSA	M21-M33	B6HS
	B33	B7HS
	B34 Iron head	B7HS
	B34 Aluminium head	B7ES
	B34 GS Clubman	B8ES
	B40 B44 B50	B7ES
	500-650 Twins - Later	B7ES - B8ES

Norton	250 - 400	BP7ES
	M50 - ES2	B7ES
	500 to 750 twins - Commando	B7ES

Triumph	3T 46-51	B7HS
	T100 early iron	B7HS
	6T iron to '60	B7HS
	T100 Aluminium to '59	B7ES
	T90 - T100 to '73	B7ES - B8ES

Velocette	MAC - MSS	B7ES
	Viper - Venom	B8ES

calc

A tuned engine, e.g. raised compression, may need a harder than standard plug.

A general guide to plug manufacturers equivalents.

	NGK	KLG	CHAMPION	AC	AUTOLITE	BOSCH	LODGE
Softer	BR6ES	FE70	N5, N6, N84	45XL, 45N	AG4	W145T2	HBLN
	BR7ES	FE75	N4, N88	44XL, 44N	AG3	W160T2	HLN
	B8HS	F80	L5, L81	42F	AE2	W240T1	2HN
Harder	B8ES, B9ES	FE80	N3	43XL, 43N	AG2	W240T2	2HLN

A good article on spark plugs and heat ranges can be found on the NGK website at the following link:

http://www.ngksparkplugs.com/techinfo/spark_plugs/techtips.asp?nav=31000&country=US

Telephone: 01234 880605

Email: bthcomponents@gmail.com