This listing offers a modern reproduction of the original KLG 18mm 'Long Reach' ML50 spark plug, of a similar type to those fitted to Douglas 2 3/4hp models (if fitted with 18mm plugs) and some early Norton single cylinder models - i.e. the WD16H, as shown in the photographs. This listing also offers both 14mm and 18mm modern copper/asbestos type crushable washers for spark plugs
18mm 'Long Reach' type KLG ML50 Spark Plugs:
For anyone that has searched for the 'Long Reach' (0.750") type 18mm plugs that were fitted to some older (pre-WWII) motorcycles or cars, they will know this longer reach type are now extremely hard to find - most 18mm types now available being a shorter 0.5" inch length - which although can be fitted, can upset the combustion and timing slightly.
We have a small quantity of these KLG ML50 type spark plugs with the correct 0.750" 18mm thread, which have been reproduced by a specialist spark plug supplier in the last 5 years.
This type of long reach 18mm plug was of the type fitted to both Douglas 2 3/4hp models (if fitted with 18mm plugs) and some early Norton single cylinder models. I know this type was fitted to Norton WD16H models - and in the accompanying photographs you can see one of these plugs fitted to an original 1938 manufactured Norton WD16H cylinder head. I do not have any other earlier Norton 18mm heads myself - but would expect this type of 18mm/0.750" spark plug hole was likely to have been used on earlier Side Valve models and maybe some 1920’s OHV models? . . I expect if you own of these you will know yourself if it requires this type of plug.
Please note: as supplied, the plugs are fitted with the normal brass 'bullet' style HT lead connector - i.e. of the type to accept a bakelite/plastic spark plug type. However, if like me - you want to use them with an older style brass HT lead connector - we also manufacture the knurled screw on connectors in both 'Champion' (0895_5) and larger 'Lodge' type (0895_2)- see Item Listing 0895, and one of them is fitted in some of the photographs in this listing. We also manufacture the very pretty brass 'Lodge' type early 'cooling fin' and locknut (0895_8), which will nicely fit over this plug - to give an even more period look to the spark plug!. These items can be purchased separately.
The background to my search for this type of spark plug, is that I wanted to fit new 18mm plugs to my Douglas 2 3/4hp restoration project. I have original Valve caps for this model with both 14mm and 18mm threads - but wanted to fit a more period 18mm plug. As you can see in the accompanying photographs - they look very period and pretty fitted (and if you are a Douglas 2 3/4hp owner, note that we also CNC manufacture the valve caps shown here in stainless steel, as original pattern, which can be purchased in our Douglas section - Item 0897)
Update September 2021: I am sorry to say these have very quickly gone out of stock and talking to the manufacturer - these are looking like they may be a Covid casualty, in that we are now struggling to get a further batch. I am currently looking at alternatives and will update this listing shortly - you can email on email@example.com for updates
All other washers listed below are still available
0896_2/3/4 - Crushable Spark Plug Washers:
If like me, you have numerous 'New Old Stock' spark plugs - but they have lost their original 'copper/abestos' type washer (with the distinctive copper colour), we can now supply them in both 14mm and 18mm sizes - in packs of six. The 18mm size have two thicknesses - the wider type being slightly more expensive (and sold as a pair) - but the slimmer 18mm type are still usable and worth keeping some in your toolbox in case you lose one on a run. You would normally replace these washers each time you remove the spark plug (unlike modern steel spark plug washers) – so it is worth keeping some in your toolkit
Note: Originally these heat resistant 'crushable' type washers were copper with asbestos filling - these modern ones no longer use asbestos - but instead a modern safer filling!
If we find any other modern reproductions of the older style veteran 18mm or 14mm plugs we will add them to this listing - please email us on firstname.lastname@example.org if you know of anyone manufacturing them, thanks.