Hi All
I was recently given a copy of an original KLG Sparking Plug chart illustrating only KLG Mica plugs. I run most of my early machines on these plugs which are attractive with their polished brown mica insulation with a brass band on top. They are also detachable for easy cleaning. Interestingly in recent postings there was discussion on the "reach" of plugs and whether performance would be better with plugs that actually reach the combustion chamber. Well, according to the KLG Chart they only recommend one plug to suit all road going Douglas machines and that is Type K1 and this happens to be their shortest reach plug. (For sports models they recommend type KS5 which is also very short reach)
Over the years collecting these KLG plugs I have picked up a few other grades, some with longer bodies and/or with longer reach but I cannot honestly say that I have ever noticed any difference in performance. My view is that in slow revving, low compression side-valve engines with the usual Douglas variations between cylinder barrels of combustion chamber volume and casting thickness it does not matter a darn as long as you get sparks, even from 80 year old antique sparking plugs. No doubt this will get some people excited.
Regards Chris.