sometimes on startup i flood the engine and then it wont start or it wont rev. Tonight out of shear anger and after many push starts i turned the fuel key to off and tried it and it kicked over almost straight away and started to rev. i then set it back to main and off i went. hope this helps
another option is to hold the throttle open for a while, and / or start the bike when the throttle is open. Ideally one won't flood the engine to start with, but this works as does deanes suggestion.
