I've found the problem. The spark plug I'd arcing against the radiator baffles on the engine. New lead? The spark plug looks fine with no scorching on it and the lead looks good on the outside.
I have a 61 plate YBR which has just started hunting between 1000-2000 rpm and then stalls. Any idea what can cause this? My local dealer has never heard of this happening before.
It has done 530 miles from new and has always been garaged when not in use.
Any help will be gratefully received.