yes i agree with stoobie, check the connections under the tank.
if you disconnect the 6 pin connector from the starter button, use a multimeter across the black and blue/white wires and make sure you get a short circuit when you press the starter button, if not you may need to open the switch housing and clean the contacts of the starter button itself.
atleast the problem is not in the alarm or cut off circuit cos that could be a pita if your not that familiar with electrics.
good luck