I'd check your starter solenoid first because you said it strikes an arc as soon as you touch the the battery and it tries to start the motor. Was the key on or off? Surely if you were changing the battery out your key was turned off. If off, then check the solenoid, if the key is on then check the starter button. Also if the key is on, flip your engin kill switch on you bars to off and that will kill the operation of the starter button also. My money is on a stuck starter soleniod. just my $.02