Yep AVB whenever I have a motor with a running issue I like to use a second hand plug out of a mower that I know has no problems as
sometimes you can get caught out with new plugs that won't run properly.
That's strange Norm if it worked the first time ,If it doesn't kick back with the plug lead disconnected it may be fixed by slightly retarding the ignition ,you could take the flywheel key out and see if a little retarding of the spark fixes it ,if it does just file the key on the side to retard the ignition and move the flywheel into position before tightening the flywheel nut but sounds like you are getting fed up with this one.
I think I read somewhere that with different Honda small engines they can have more advance than others.
