98 explorer 400...battery was shot...replaced with a fresh battery. Ran the ATV for a few hours...next day frozen dead battery. It was a cheap Wally world battery...figured it was just.junk. purchased a yuasa (sp?)
Ran great...next day...dead! Just put a multi meter on it after a fresh charge. 12v. Fire it up and get 14v...give it some gas and get 17.5v!

I assume its the.voltage regulator? Thought?

 

Regulator/rectifier's overcharging the battery. Batteries will heat up and bubble out the vent tube if a conventional battery or will just dry up and short the cells out in maintenance free batteries. Have had that happen several times. They can under charge or overcharge.Here's one place to get a new one. http://www.regulatorrectifier.com/catalog/Polaris-67
Here's the other one. http://www.psep.biz/store/polaris_at..._regulator.htm
According to the manual you can test the yellow and yellow/red wires from the stator.Set the meter on amps and recoil start only and have at an idle. Should be around 5 amps.

 

Thanks opt.

Did some trouble shooting today...found the connector w/ red/brown wire to be the issue. Both corroded...red connection corroded through and broke. A few new connectors and some shrink tube... good to go. 13/14 volts at idle/3k.

 

Strange? Usually this would cause an under or no charge condition back to the battery. As long as you found the problem and it's charging correctly that's all that matters! Good luck.