Just look at "Saving_old_Seaguls" site already referred to. Lots of hints and tips on fixing engines. Mind-you, He's not keen on dismantling - recons most things can be fixed without!
Just to round off: Thanks to Saving Old Seagulls I've solved the starting problem. The upshot was the ignition timing was way out, and my engine seems to a have a mechanical oddity meaning the normal alignment hole was in the wrong place. It now starts and runs beautifully, so I take back all I said about traditional British engines.
Stopping is no problem either - just throttle right down, and it stops. So simple!
How odd.
Somone must have been mucking about with it in the past!
Anyway glad to here the news. /forums/images/graemlins/cool.gif
Wondered why that dirty great cloud of smoke, came wafting in from The West the other day!