Misc: Ignition/Mag-Dynos Spark Plug

[Stanley Chappell]

Simple question - what is the correct plug for Series 'A' Comet?

Many thanks - Stanley Chappell

 

[Peter Holmes]

Paul Richardson, KLG F70, one for sale on ebay right now for £12.00, far better than all the modern offerings.

 

[oexing]

For old magneto ignitions try to get spark plugs without resistor in the plug. Most of modern plugs got resistors in plugs and other places for electronic emiission control. But this produces weak sparks on Lucas gear. With Bosch Plugs it is marked as WR 7 on plugs , with R meaning resistor. So when in doubt , check plugs for nil resistance . Otherwise I do not buy OWTs about fake plugs all over the place. My guess, riders keep buying handbook plugs with unsuitable grade for their kind of ride today - which is mostly just pottering around . And from this they get black sooty plugs with troubles then.

Vic

 

[Peter Holmes]

I agree with Vic’s advice on resistor spark plugs, do not use them, I do not agree that the original grades of plugs as suggested in the handbook are not good for modern riding conditions, they are, I only ever use KLG FE70 plugs in my post war Vincents and they were work really well, reliable, long lasting, perfect, and I ride in modern conditions (regrettably!)

 

[roy the mechanic]

It depends on which type of head you have. Original 14 mm will be b6hs, modern 10mm c6hs.Thats in n g k .

 

[royrobertson]

I think It's worth looking at Brisk plugs. They are supposed to be more suitable in our old engines. I run them in my 1971 Commando and 1964 AJS single and they are not expensive. I think they are made in the Czech Republic.
roy the racer

 

[John Oakes]

My series a meteor is running very nicely with a champion L 10. New ones available from green spark plug Co.

 

[Alyson]

For old magneto ignitions try to get spark plugs without resistor in the plug. Most of modern plugs got resistors in plugs and other places for electronic emiission control. But this produces weak sparks on Lucas gear. With Bosch Plugs it is marked as WR 7 on plugs , with R meaning resistor. So when in doubt , check plugs for nil resistance . Otherwise I do not buy OWTs about fake plugs all over the place. My guess, riders keep buying handbook plugs with unsuitable grade for their kind of ride today - which is mostly just pottering around . And from this they get black sooty plugs with troubles then.

Vic

not just the plug, but the cap too. Make sure your cap is not of the resistor type. If they are, they will be marked on the side with a value and ohms.

 

[Peter Holmes]

If you are not hung up on originality, NGK make a really good black non resistor plug cap, you do not use the screw on plug top, the NGK cap goes straight onto the threaded part of the plug, which I think is a good thing.

P.S. It looks like the Club Spares sell the NGK spark plug cap as an unspecified manufacturer, but it is definitely NGK and unsuppressed.

 

[Marvel]

NGK BP6ES works for me.
B = 13/16”AF hexagon
P = projected insulator less likely to oil up
6 = heat range between KLG FE70 and 80
E = 3/4” reach seems right for my bronze head
S = 2.5mm copper core