I'm having trouble with the starter on my bike. It only seems to do it when the bike has been sitting for a few hours or more. When I turn the key to the on position, I can hear a whirring sound, which I assume is the fuel pump priming, but when I hit the starter button, I just get a very similar whirring noise and nothing else. Sometime a few presses of the button with get it to actually turn the motor over, and sometimes I have to rock the bike with it in gear to get anything to engage. It get's harder ever day though to get the starter to engage. Anyone know what can be the cause of this?