Like posted above, remove the plug boot form the end of the wire and cut 1/4 inch off the end of the wire, then screw the plug boot back on. Gives you a new connection. If that doesn't help, swap a coil from one of the good cylinders to the one in question. If the problem follows the coil, then you need a new coil.
Also, just make sure your carbs are cleaned and it has fresh gas and plugs. A little water/old gas and almost fouled plugs will obviously run like $hit too. Good luck
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