misfire that won't go away..

[ade the blade]

my money is still on electrical. if it was fuel then you`d possibly have terrible probs just starting it ! are you getting a nice meaty spark from lead for that plug as strong as the others, if so, is it constant? try trimming back the lead end a little bit. seems strange how it can fire up on the button and then run rough.  :'( perhaps that coil pack is breaking up ( think it `sparks` #1 lead too ) play about with the leccy side mate only other possibility is water / condense in #4 float bowl. how much new fuel have you run through the carbs?