Further to our spark plug article on maintenance and fitment from many a year ago (Motorcycle Sparkplug Conundrum 2010) here is an update with the inclusion of the listings from Lodge. The information is from 1948 and covers most of the early motorcycle makes. Despite what the cover says I have only included the motorcycle section of listings (and the piece of string holding it together).
Probably the most informative of all is the heat range chart which I have extrapalated and displayed below. It will show where in the Hot~Cold heat range that box of new plugs that you bought from an autojumble for $1.00 fit and will save you the time of having to wander through the listings to see what is there.
Click on the front cover below to see what you could be using in your motorcycle.
It is a 2.37M PDF and you will need Adobe Acrobat Reader to view it.