Fist thing to look for see if the Main Ground wire located next to the Starter is tight.
Now look for the Handle bar Switch connectors and unplug them, using a Multimeter to probe all the wires I mention below...
Now to Check your handle bar switch, unplug it from the Harness, make sure the Kill switch has no continuity when it's in the "Run" postion meaning your Multimeter should only make a (Beep) when the kill switch is switched off, those are the Green wire and Black/White wire. They "Connect" when you shut off the bike.
Check the Start Button it should have Continuty Yellow/Red and Black "Connect" or Multimeter "Beeps" when buttonit pressed.
Next check you the Main Key Switch. Unplug the Key Switch and using a your Multimeter, when the key switch is off you SHOULD have Continuity "wires connect" between the Black/White & Green (Multimeter beeps)
With the Key on you SHOULD have Continuity between the Red and Black (Multimeter Beep)
Another thing you can also try is cutting the 2 Black wires on the Caburertor and tie them together see if it fires.
