I'd check voltage to the coil.
If you have an inductive timing light, hook it up to the plug wire and see if it's got a reading. Can also remove the spark plug cap and lay it against the engine. The spark should have no problem jumping from the cap to the motor.
Might want to check the plug. I found this on my Vstrom a few years back.
...dual plugged heads meant the bike ran OK, just sounded funny.