Yamaha YFZ450 Charging System - No Spark

You've tested the regulator-rectifier and stator of your Yamaha ATV but you still have no spark. When you test the charging system on a Yamaha YFZ450 for a no-spark condition, what else should you look for? 

Our resident Yamaha ATV expert John Talley does live Q&A sessions on our YouTube channel every Friday at 3pm Eastern. In this edition, John gives his thoughts about a YFZ450 that's being tested for a no-spark condition. 

Yamaha ATV

My YFZ450 regulator-rectifier has two wires coming out of it, a red and a black one. No matter what OHM setting I put it on, the multimeter shows OL, but on the other wires that plug into the stator connection, it shows the 20 ohm setting. Could this be the cause of my no-spark condition? Keep in mind this bike doesn’t have a battery. 

John Talley: If it doesn’t have a battery, it has a capacitor in there that temporarily stores electricity because it really doesn’t use much, and your black and red wires are pretty much representative of quote-quote “battery voltage”, although you can’t measure it because it’s just a capacitor and it charges and discharges very quickly. Now you’re looking into your stator and you’re seeing a 20 ohm. I can believe that as far as the resistance that you’re going to see because that’s reading back into the coil going around the stator. But is that causing your no-spark? I doubt it. On that particular machine it’s pretty easy to diagnose. If you’ve got an OL on your red and black wires on the 20 ohm setting, that tells me your charging system should be ok and more than likely it’s going to be your ECU or CDI. Because there’s nothing else to go wrong. Are you sure your spark plug wires and your spark plugs are good to go? Take a look at those as well. 

Watch the video below to learn how to test the charging system of a Yamaha YFZ450 ATV.

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