There was a club jumble quite close by in Helchteren today. I didn't find any Norton stuff (but I'm not actively looking at the moment).
However, I did pick up a nice boxed KLG screw-down 'waterproof'plug cap and a box of chain spares in remarkably good condition.
The cap is threaded 3BA
The box states that it is suitable for all 'K' type plugs, presumably including the KS5 fitted to Nortons and the internal diameter reflects the cooling rings on this type. Does the M20 use a smaller cap for the 14mm 'L' type plug ?
I seem to have become a KLG collector without even realising it was happening...
Very nice to have that cap with its original box Rik. They are definitely correct for C10's and M20's. I've never noticed them on Norton's? It does seem a bit pointless to fit cooling fins and then cover them with that cap. Ron