first thing you need to do is see what cylinder is not firing or miss firing.
start the bike and take a damp rag and touch the pipes where they come out of each cylinder and see what pipe DOES NOT sizzle the water on the rag, they will get hot very quickly and warm does not count!
pull that spark plug wire off that dead cylinder and stick a good plug into the loose plug wire and restart it while grounding the base of the plug to metal. to verify good spark.
the spark plug cap itself is replaceable from the of the coil wire #4xy-82370-00-00 , they can often get a fine hairline crack in them and make this type of concern.
they are screwed into the end of the wire and easy to remove.
best of luck, hope this helps
Mike:080402gudl_prv: