Katana 600 not starting but headlights are on

[Jaybird_101]

Hey guys. I bought a used 2006 Katana 600 because it was cheap and I figured I can turn it into a project bike and learn how to work on them while in grad school.

I took apart a ton of stuff because it seems the previous owner(s) didn't take care of the bike. I'm putting it back together and when I tried to turn the bike on to sync the carbs, it wouldn't turn on. If I turn the key, the headlights come on. When I hit the start switch, the lights turn off (till I let go of switch) but there's no noise at all.

I'm using the battery that came with it. It's a Walmart battery and I don't really trust it. I kept it on a smart charger for 3 days and the charger said the battery should be fine. But a voltmeter said:

12.05v voltmeter leads attached, bike off
11.37v key switched on
11.71v start switch pressed and held

Battery charts say 12.05v should be 50% charged but I don't trust that in the cold Philly weather.

Does a battery replacement seem like a good place to start? I don't know much about electronics, but this'll be a learning experience.

[WestBrantKid]

Sorry, but I'm not good with electrical systems myself, but I can say that the first thing I usually do when I get a new bike is replace the battery. So that wouldn't hurt. Then you can diagnose if you still have issues.
I'd also double check all the plugs and wiring are connected. Maybe it's as simple as you missed a plug.