I kinda touched on this in your other thread where the bike died on you.
With the electronic ignition in these bikes, the module needs a minimum voltage for it to fire the spark plugs. With a new battery while you are cranking the starter the battery stays close to 12V and the ignition module works great.
If the battery gets old and weak the huge load of cranking the starter pulls the voltage down. If the battery is pulled down below about 10V, the ignition module just shuts off and you get no spark. It can be hard to tell that the starter is cranking a little slower, unless you are really use to how the bike normally sounds. The starter has no minimum voltage, it will crank the engine over slower and slower:
10Volts... 8V...6V... 4V... you can drain the battery right down almost to nothing.
If you ever get in the situation where the bike wont start and it sounds like the starter is going slower than normal, you can push start a 650 fairly easy. Down a little bit of driveway or down a slight hill, if you can get the bike coasting up to 10 or 15mph or more in neutral, with the ignition on, the kill switch set to LIVE, gas on, choke out for a stone cold engine, then pull the clutch in, kick it up into 2nd gear, and let the clutch out smoothly. The engine should start right up, so just keep going, and know that its time for a new battery
with your vmax or other heavier bikes you might need a little longer hill to get up to 15 or 20mph in neutral, before you kick it up to 2nd gear - just because a bigger engine will take more inertia to spin it up.
Last edited by KCW; 10-19-2018 at 08:40 PM.