OK used to work on atv's for a living and this is the first time i've seen this. Just bought this bike used. Started it at the dealer and it ran fine. Got it home won't start. Pull spark plug and I have no spark try new spark plug and it sparks only 1 time and after you let go of the starter button. It's a couple of seconds later and it decides it wants to spark. Every once in awhile it will spark good but as soon as I put the plug back in I'm back to no spark until I let go of the starter. Cut the the spark wire and tried a differant cap but no luck. Weirdest thing I've ever seen.

 

Check the resistance across the starter solenoid. I've seen this problem before. You may have to replace the solenoid.