I hope that someone can help me. I have a 1939 bsa m20 side valve bike. I am looking for a spark plug for the bike. does anyone know what a current ngk sparkplug should be used for this bike? also, what is the correct plug gap for the plug?
I run a BP5HS in mine. one grade hotter than Ian and projecting deeper into thte combustion chamber as there is not much chance of hitting the piston.
We get really bad "fuel" ( which is not petrol ) down here. I oft call it John West ( the fuel the rest of the world rejects ).