1933 Model 18 Norton

[ragworm]

Hello,

First post, hope you can help, can anyone recommend an 18mm spark plug suitable for my 1933 model 18 Norton, I ride it quite hard and where in England might I buy one.

Thanks and best regards,

Pete

[L.A.B.]

I believe the original plug would have been a Lodge H1?

But what are you using now?

Is it a plug type that is now unavailable (could it actually be a Lodge H1?).

The modern alternative to the H1 would seem to be a Champion K8G available from:http://www.gsparkplug.com/

[ragworm]

Hello,

I will check in the morning what the current plug is, cannot remembr off hand, my documentation lists the H1 for normal riding and H45 for hard riding, I use my bike quite hard so would look to the modern equivalent of the H45, but, I would settle for the H1 equivalent if that was what is available, any suggestions will be welcome.

I have rebuilt the engine, had the mag overhauled and would like to put in a nice new plug of the correct type.....

Thanks,

Pete

[L.A.B.]

I think this gentleman (Dr. George Cohen) could possibly advise?:http://www.norton.uk.com/

[lsdt]

Taken from the book "Motor Cycle Maintenance and Repair" all Norton models from 1932 by Norton's EM Franks.
1932 Model 18.
comp 6.2:1
Ign 5/8"  BTDC fully advanced
valve inlet timing opens BTDC 1/4"
exhaust closes ATDC 1/4"
tappets cold inlet 0.002" ex 0.004"
piston ring gap comp 0.020" scraper0.008"
plug lodge H.1

Models 50 and 55 with 7:1 compression also use the lodge H.1
I've lost the equivelants page from "Speed and how to obtain it"third edition, but the author mentions fitting a threaded adaptor to fit better racing plugs.

For 1937 SV and OHV models Franks quotes the KLG F100 and Lodge HHN both 14mm for OHV. Sidevales KLG M80 and Lodge H3 both 18mm.
I hope this is of some help.

[ragworm]

Thanks for the reply, I have all the Franks and Pitman books which list what was used with regard to plugs, what I was looking for was a recommendation as to a modern equivalent that is readily available, or even new old stock that is avilable, a plug that riders have been using lately and are happy with, just a thought. I could ask George Cohen but that would be too easy, this seemed like a site that might have some good answers....

Thanks,

Pete

[33d6]

NGK make a really good 18mm plug. The heat range of modern plugs is so much broader than those when your bikre was new that it makes selecting an effective plug much easier. I'd start off with an NGK A4 and go upwards to an A5 or A6 if necessary but that shouldn't be necessary unless you try a non stop flat out run to Monte Carlo in mid summer. Buying individual 18mm plugs can be tricky. Where I live in Oz its easier to order in a box of a dozen NGK than find somewhere selling singletons.
Best of luck, Bob

[ragworm]

Hello Bob

Thanks for that, onwards and upwards, NGK's here I come

Best regards,

Pete