I'll reply on the oil issue as poor Mr. Fastback hasn't had his worries about what oil to use allayed yet. The main issue as I see it with high detergent oil in old style engines is that these engines were often designed with built in sludge traps (this is in the centre of the crankshaft in Nortons) to separate out the solids that accumulated within the oil. High detergent oil is somewhat likely to dislodge some of these solids if put in an old engine, leading to possible damage. However if an old style engine is newly rebuilt and has no solids inside then high detergent oil will keep any new deposits in suspension until the oil is changed at the next interval. Modern fuels do not seem to produce as much in the way of solid deposits as old fuels did, hence regular decoking of heads and pistons is now largely a thing of the past. The only thing I will say about modern oil is that our ancient machines have much bigger tolerances within the moving parts than modern machinery, so my own preference if I use multigrade oils is to go for a 20'50 grade rather than a 5/30 or 10/40 for example.
