Yep you are all on the right lines.Now I won't clash with Oilman or the other experts if I can avoid it as I'm no expert in anything.
My 'R' days started when I bought X Harold Daniels Norton International, single cylinder 500c.c. bevel gear drive ohc. complete with Brooklands reverse cone megaphone silencer and garden gate frame. And yes it had exposed hairpin valve springs, with exposed valve stems and felt oil seals that sort of just soaked the oil up, the residue running back through drillings in the head, and the rest flew out over my Mike Hailwood boots. So at least they were fully waterproof.
Engine needed a strip down to wash the burnt on lacquer off with methylated spirit periodically. Oh how the Goldie' and Venom singlers envied my flaming exhaust with just 1/2" chicken wire as it's baffles, but they envied my wonderful perfume more than anything as I revved her up. Like armoore says some put a cupful in their fuel tanks to emulate the smell, but the poor old retards had to use Castrol XXL as the preferred lube for their inferior machinery iirc
. Only joking Goldie and Venom boy's they were brilliant thumpers too.
Quite a few of the two wheeled grass cutting two stroke boys, (mods on scooters) would add a spot of brake fluid to their fuel tanks to get a similar stink. Dunno what that did to the motors? Probably kept the transfer ports clean?
I really need to get a life now, as my youth was so bl**dy boring! You lucky young things.