Sometimes the spark can jump the electrode and will look like there isnt one, best way to make 100% sure is get little sister, wife or girl freind to hold said spark plug while you kick, this is a 100% sure fire way to see if you do or do not have a spark.

Ive found on two mc21 harness now (one hrc one) a very blackened connector going into the left hand pgm connector (white 16 pin) which killed a spark.
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If I have to take the carbs off once more...