Electrical issues after sitting for years

[Feral Ghoul 93]

My neighbor gave me his old 2004 Polaris Sportsman 600 to fix up and I'm trying to get it back in shape without spending a fortune. The battery won't hold a charge and the lights flicker when you rev it, which makes me think it's more than just the battery. I already cleaned up the grounds and checked the stator output but I'm not sure what else to test. He said it sat for two years in a shed, so I wouldn't be surprised if mice chewed something. Any tips on cheap diagnostic tools or places to get used parts?

 

[Erwann91]

It could be a battery issue, might be tied to the stator or wiring if the lights flicker when revving. Since itss been sitting for a couple of years, check all wiring for chewed or corroded spots, especially around connectors. For cheap diagnostics, a multimeter and continuity tester go a long way, and you can often find used Polaris parts from local salvage yards or online forums like ebay and ATV-specific classifieds. Have you tried testing the rectifier/regulator yet?

 

[Feral Ghoul 93]

Checking the rectifier or regulator sounds like a good next step, since a problem there could explain why the battery isn't charging and the lights are flickering. I've looked over the wiring and didn't see any obvious issues, so now I'm focusing on the charging system. What's the right way to test the regulator on these ATVs? Do I just check the voltage at the battery while revving the engine? I'm hoping to get this fixed so my neighbor can enjoy his old ATV again.