I have one of these -

Its an ancient (non recoil start) Norton Villiers F15 Side Valve 4 Stroke, with B10 Carb.
When i got it, it had no compression at all. Took the head off, and, sure enough, stuck valve.
Worked that, and now opens and closes fine. Will spin in the guide, but the top of the pison, valves, all looked pretty mucky, so im not sure how well the valve is seating (seems ok, but i just dont know how much compression it should have, and have no tools to measure). Cylinder bore looked fine.
Anyhow, i still cant get it to start.
Its not easy (for me) to pull a non-recoil starter, and look at the spark at the same time, but i alreddy managed to make myself jump, electric fence style, so i assume something is kind of working there.
So, then onto the carb -
The throttle linkage does nothing at all. The carb seems to be sprung in the same way as the linkage from the 'handle bar' control pulls. Ie the carb is naturally sprung one way, and the linkage just tries to pull it the same way - which evidently cant be right.
But that's as far as ive got.
This is the beast the engine is on (well, off, at the moment) -

(ive just sorted the hydraulics for the trowel profile, so im now keener on getting the engine sorted)