If you have looked at this listing before (i.e. prior to October 2021) you will have seen that we were able to offer a modern reproduction of the original spec KLG ML50 - which had the correct (and now very difficult to find) 18mm 'Long Type' thread, which was 0.750" in length, as was originally fitted to some Norton models (i.e. WD16H Norton and the early Douglas 2 34hp and 3.5hp models). Unfortunately, these have now all sold and our manufacturer supplier tells us that (partly due to Covid impact) they are not likely to have another batch made, so are now unavailable - sorry.
However, having talked to this spark plug specialist, I am told that there are modern 18mm 'Short Length' spark plugs available (i.e. 0.5" length thread), and these will still work in a cylinder head with 0.750" thread length - and in fact it was quite common for this length plug to be fitted even in period times. Therefore, we now offer two modern Champion alternatives in this listing - both in 0.5" thread length and will continue to add if other types come available.
We are also looking at the possibility of converting a quantity of 'New Old Stock' KLG WW2 18mm WD aircraft spark plugs (with 0.750" threads) to a suitable motorcycle spec - as they currently have the aircraft style suppression tops. Email us on firstname.lastname@example.org, if interested, we will update this listing at a later date if successful
Finally, this listing also offers both 14mm and 18mm modern copper/asbestos type crushable washers for spark plugs
Spark Plug Types:
0896_5 Champion D14 - 0.5" Thread Length. Normal Running for Side Valve Engines:
These are modern 18mm 0.5" reach plugs, made by reputable manufacturer Champion - and the D14 variant is considered the best choice of grades for a Side Valve engine in normal running condition. As 0.750" reach plugs are now unobtainable - these provide a suitable alternative, and according to our supplier - were often fitted to those engines with an 0.750" length spark plug hole even in period times.
0896_6 Champion D16 - 0.5" Thread Length. Oily or Rich Running for Side Valve Engines:
These are modern 18mm 0.5" reach plugs, made by reputable manufacturer Champion - and the D16 variant is considered the best choice of grades for a Side Valve engine if your engine runs rich or often oils plugs. As 0.750" reach plugs are now unobtainable - these provide a suitable alternative, and according to our supplier - were often fitted to those engines with an 0.750" length spark plug hole even in period times.
For the two plug types above (the same type of plug - but with a fractionally different heat settings - it may be prudent to take one of each type and find which is best for your own engine, if you are not sure which you require.
0896_1 KLG ML50 - 0.75" Thread Length. (Sorry now unobtainable):
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. 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.
Update September 2021 - Very sorry, but our suppliier has now ran out of this plug - and is not expecting to have another batch manufactured (partly due to cost increases post Covid). I have kept the listing here, in case this changes in the future - and will update it if a new batch are to be manufactured in the future
0896_7 KLG RML 60 - 0.75" Thread Length. (Oct 2021 Enquiry Only - but possible special order):
As at October 2021 - we are looking at the option of converting a quantity of 'New Old Stock' WW2 military aircraft KLG spark plugs - which also have the longer 0.750" length spark plug thread, as fitted to the models described above. As can be seen in the photograph - as originally manufactured they have a special 'aircraft type' suppressor fitting - and will not accept a standard motor cycle style HT Cap. We are currently looking at re-manufacturing the top of these to fit a motor vehicle style insulator and central core, so they will accept a standard HT Cap or screw on knurled top. If interested - please email email@example.com - but expect the price to reflect the work required to re-manufacture these, and their rarity
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/asbestos' 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.