bt-h logoBT-H Magnetos Ltd.bt-h logo

Home Contact Us Magnetos FAQ's BT-H Racing Marque / Model Rider comments Plug Types For Sale Fitting Instructions Links Interesting Articles

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 large gap is not necessary unless you have plug fouling problems.

N.B.  Our local dyno expert 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: 01455 844244    (Daytime best before 2.00pm) 
                                                    (Evening: 01455 457382 - 6.00 p.m. to 7.30 p.m. only)    

FAX: Please telephone our daytime number first. 

Copyright © 2008 E. Grew