Misfire when rolling on the throttle.

[peteski]

Update - Carbs stripped down and cleaned last week, all passages blown through, diagrams are all intact and jets clear. The sun had gone down when I'd finished so I took it up the road and back to see if it had made any difference. At low revs it was only running on three cylinders and almost stalled pulling away. Disheartened, it when back in the garage and I headed inside. The next night after work I started it and felt the temperature of each header, all were getting hot and this time sounded just fine. Took it out for a longer run to the petrol station to fill up and it ran smoothly. I can't say if the problem is gone or not as it used to come and go, some days worse than others. Time will tell I guess.