Why Do My Yamaha ATV Lights Only Work Sometimes?

What does it mean when the lights on your Yamaha ATV only work when you reach a certain speed, even after you replaced the stator? Could the problem be the regulator rectifier?  

Partzilla’s Yamaha ATV expert John Talley hosts live Q&A sessions on our YouTube channel every Friday at 3pm Eastern. In this session, John was asked why the lights on a Yamaha YFZ450 only work when the ATV reaches a certain speed. 

Yamaha YFZ450 Lights Not Working Q&A

I have a Yamaha YFZ450, and the lights won’t turn on until I rev it up to a certain RPM. I replaced the stator and that didn’t fix it. Any suggestions?

John Talley: Alright, well I would be curious to know what kind of voltage you have at your battery with it running. Most of the time the problem is not the stator. Ninety-five percent of the time it’s the regulator rectifier. My son has a YFZ450R, and we had a problem with it. I can’t remember the tell-tale signs, I mean, he’s had it for about 8 years now, but it had something to do with the lights as well. But the problem ended up being the regulator rectifier, even though it bench-tested fine, so look into that. 

Watch the video below to see how to troubleshoot electrical problems with a Yamaha YFZ450 ATV.

Watch the video below to learn how to test powersports vehicle regulator rectifiers.

Watch the video below to learn about choosing the best headlights for your ATV.

Want to see more live repair questions answered? See more motorcycle and ATV repair questions answered here.