Yamaha 350 Big Bear

[IAfarmguy]

I am having trouble with the charging system on this atv. The (not particularly old) battery was replaced earlier this spring. It acts like the Yamaha isn’t charging the battery. What sort of charging mechanism does Yamaha use and how can I fix it. I managed to get it started a couple days ago, drove a couple miles all over the farm for a hour or so doing some scouting and after parking in the shed the electrical system wouldn’t even click the starter. Thanks.

 

[MarkB_MI]

I've never been into the charging system on that ATV, although I've worked on my son's Big Bear. But most motorcycles and ATVs of that vintage use similar charging systems. There's a three-phase stator that's powered by magnets in the flywheel, and a shunting-type voltage regulator/rectifier. The regulator allows the voltage on each phase to rise to certain level, then that phase is shorted ('shunted') out.

First off, confirm that the ATV isn't actually charging, as you might just have a bad battery. Check the voltage at the battery with the engine running; it should be over 13 volts; probably 14 volts or more. If the voltage is low the charging system isn't working.

Look for the regulator and disconnect it. You'll then be able to check the stator for continuity between each of the stator's phases. You can also check the stator's output voltage when the engine is running; it's probably around 90 volts AC. If the stator appears to be good then the regulator/rectifier is likely bad.

 

[BarnyardEngineering]

First thing you need to do is find your multimeter, or buy one if you don't have one. Even the cheap $8 Harbor Freight one. Verify your battery voltage. A couple of hours of running should not run down the battery.

My brother in law's Grizzly had a similar problem with starting and it wasn't the battery. It would just click when he tried to start it. It was a relay or the solenoid or something like that...

What Mark said above is pretty much it in a nutshell for the charging system, a stator under the flywheel with a regulator. You can probably find a youtube video showing where and how to access all of it. Not going to be as simple as changing an alternator.