I have a used 110cc atv that I finally got running. I had to bypass the kill switch and wire a new push button start straight to the solenoid. However the first week the battery was fine. Now it seems like the battery is being drained overnight. Its a brand new battery. My first though is that If i unplug the regulator that's plugged up maybe that would do the trick however nope nothing changed battery still drained. So should the regulator be replaced because the atv does have lights but we never use since its only being ran during daytime hours. Before i start tearing away wires looking for some options

 

First find out if you do have a drain by disconnecting one battery terminal and connecting a 10amp ammeter between the terminal and lead, with ignition switch off, a drain of .1 of an amp is too much. If it does have a drain, disconnect the regulator and see if the drain goes away. Also check the bike is charging, by putting a voltmeter across the battery with the engine running, it should be more than with the engine stopped, though many of these little bikes don't charge much over 13v.

 

I had a similar issue and found out that it was the light switch next to the starter. The front light switch is a three position switch and must be slid all the way to the right to have the lights off. This was causing my battery to drain.

 

It turned out to be the brake light switch. One was stuck so the light would stay on at all times. So when the atv was parked it was still pulling juice from the battery. I took the switch off. Brakes work fine so didn't impact that. The kill switch button was bypassed so didn't need to rely on the brake switch to start the atv.