Why won't my 2003 intruder vs1400 turn over?

Are you sure your bike is a 12 volt? If you are turning it over , it'll most likely flood itself in seconds. Do you smell strong gas fumes? let it sit, pull the air cleaner, and see if it is getting fuel. Pull the plug and check for oil/gas on the electrode. Is it last year's gas in the tank? Gas doesn't sit well, you may have water in your gas( just from sitting), so draining may be wise. Holding the starter will flood the heck out of the motor, as well as burn your starter to bits. Try new fuel, clean your plugs, get a proper charger/booster pack with correct volt/amps for your battery. Let your starter cool between tries, try wide open throttle Maybe your big truck battery fried a relay or start solenoid? Good luck