Hi Kevin..The magneto from a later bike could be regarded as an upgrade because of the slack advance set up. Though the reason for the change, breakage of the adv/rtd cable, is a very rare occurence. Likewise the dynamo if you are changing from a wartime one to the later, higher output type.
Theres not much in it with the gearbox...internally they are virtually identical. Further, if a later box is fitted to a girder fork bike the speedo drive in the box becomes redundant. Probably the main advantage is that apart from very early examples the later box has an oilseal fitted at the gearbox sprocket end.
However, a similar effect can be achieved by fitting a sealed bearing to the original box....Ian
Much thanks for your reply, Ian.
I was offered an M21 rolling chassis recently for a reasonable sum. The model is actually a tele front end but rigid rear. The bodywork is all missing along with the head, piston and barrel. The magdyno and transmission seem interesting to me for use in my M20 project. I assume someone here might be interested in some of my unused bits from the remainder.
Kevin
