How to Troubleshoot Yamaha ATV Electrical Problems

Riding your Yamaha ATV is quite the rush, but riding it nonstop for extended periods of time might cause electrical problems from overuse.  

Our 2009 Yamaha YFZ450R was not charging and couldn't maintain battery voltage after a weekend out on the track, so we popped it open and performed some simple charging system diagnostic tests. Here's how to diagnose and fix Yamaha ATV electrical problems.

Tools and Parts Needed - Troubleshooting Yamaha ATV Charging Problems


Check Yamaha YFZ-450R Charging Problems

Step 1. Pop the seat off, disconnect the battery, and connect your volt/ohm meter to your battery's terminals. Next, set the meter to DC volts. Your volt/ohm meter should have a voltage reading of 12.5 volts or higher. 

Yamaha ATV charging problems test

Yamaha YFZ450R volt/ohm test

Step 2. Disconnect your multimeter from the battery, and reconnect the battery to your ATV. Start your ATV and let it idle. Next, reconnect your voltage multimeter to the battery while it's running and look for the reading to increase to 14 volts or higher. 

If your voltage meter shows a decrease in voltage or no increase in voltage after firing it up, it means the electrical system is not charging. If that's the case, the next step is to check the stator, which is located on the lower left side of your machine. 

Yamaha YFZ450 electrical problems troubleshoot

Step 3. Unplug the stator and take a resistance measurement across each winding with your voltage meter set to ohms. It should measure between .32 and .48 ohms. Any measurement lower than .32 means you need to buy a new stator. Take the same measurement on the stator in AC voltage, which should read between 35 and 40 volts. Anything less than 35 also means the stator needs to be replaced. 

Yamaha YFZ450 stator test

If the stator test produces enough voltage, the next step is to pull the front panel off the ATV to check the voltage on the regulator-rectifier.

Step 4. Unplug the charging circuits that go back to the battery, which are the red and black wires on the top. 

Yamaha ATV electrical problem diagnostics

Yamaha YFZ450R regulator/rectifier test

Step 5. Set your volt/ohm meter to DC voltage before connecting it to the regulator-rectifier, and look for a voltage reading of approximately 12.5 volts. If the multimeter registers anything less than 12.5 volts, you need to buy a new regulator-rectifier.

Yamaha ATV electrical diagnosis tests

NOTE: If your regulator-rectifier tests well for a good voltage measurement but the electrical system is still not charging,Yamaha recommends replacing the regulator-rectifier anyway. Move on to Step 6 only if you bought a new regulator-rectifier. 

Step 6. Hook up your volt/ohm meter to the new regulator-rectifier, and connect the new regulator-rectifier to your machine. Your ATV should start up with the new regulator-rectifier installed, and the voltage reading should be approximately 12.5 volts. 

Yamaha YFZ450R regulator rectifier assembly

Yamaha YFZ ATV regulator-rectifier test

Step 7. Tighten the 10mm bolts that hold your new regulator-rectifier in place, and replace the front panel and the seat.  

Yamaha YFZ450r regulator rectifier installation

If testing and replacing your stator and/or regulator-rectifier don't resolve your Yamaha YFZ450R charging problems, or your ATV just won't start at all, watch the video below to see some additional electrical tests for how to check Yamaha ATV starting problems








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