This is very strange mine has a misfire as well, in mine there was a spark coming off number 4 spark plug lead right next to the ign system and arcing on the engine, going to have a look at it tomorrow and see if i can sort it hopfully it will be a plug, lead or damp if anyone knows what else it could pease post, if not i will let you know what i find. Sorry for the hijack Cheers Mike