Today I had a quick look again at the magneto. Despite a fair amount of work to clean it up and replace various parts, it still doesn’t produce a spark. I took the sprocket off and spun the mag over with a cordless drill. When rotated at speed I get a tiny spark that jumps about 1/8″ gap. Hardly the healthy spark needed for ignition!
I think further technical assistance will be required on the magneto front. Working examples do come up on eBay from time to time. Unfortunately, they don’t come cheap. Seeing as mine is more or less complete, has cleaned up ok, and is what actually came with the engine when I purchased it, I’d rather try and get this one going. Even if it does turn out to be expensive.
As the engine had sat so long without me doing anything, it had a developed a thin film of rust on the cylinder head face and also inside the bore. I used some wet & dry to clean this off and then oiled the surfaces to protect it against going rusty again. I also decided that the three brass nuts which hold the cylinder head on inside the water hopper, could do with a good clean. I gave them a going over with a file and some emery cloth, so now they actually look like brass! I applied a smear of grease to the studs as well.