you may have spark, but it might not be enough to fire the piston. swap the coil wire with the opposite plug, aka, take number one and put it on four and see if number four stops firing. Basically, see if the problem replicates on the new cylinder. That is the fastest way to find out if the coil is weak or bad.

Otherwise, I'd look into the carbs.

 

Hey guys, you're beating a dead horse here. SnoPro hasn't been back on the forum since 5-23-11.