Motorcycle Repair: regulator or battery, 2002 suzuki marauder, voltmeter

Question
I'm having trouble with my 2002 Suzuki Marauder. Sometimes it starts right away but a lot of times it cranks and if it doesn't start the first couple times the battery goes dead. I could drive it a pretty good while, stop to get gas and try to start it again and it cranks a few times then the battery gets weak and I have to start it with a booster that I keep in my saddle-bag. It always starts the first time when I hook the booster up, I just don't know which route to take battery or regulator. What do you think?

Answer
are you running as big of a cca battery as you can?
first take out your battery put it on the charger and get a good charge on it. take a reading with a voltmeter  wait till the next morning take a reading if it s lower then its bad if it stays the same try the regulator test it, if it fails that test its bad  if neither of those is bad put a voltmeter on it, take a reading start it watch the reading rev it up watch the reading it should increase as you rev it turn onn your lights rev it watch the reading compare your draw on the battery and whether or not its able to keep  recieving acharge you may have a stator /alternator problem. shorted wire etc.