Okay, how bout this scenario...putting on the kick starter and hot start setup, and yanking the starter...but leave in teh battery to help the fan...yes? Or is it still gonna melt the battery like Duncan racing was complaining about? What is it gonna take to fix that problem...different voltage regulator going back to the battery? Bigger battery (man that thing is tiny)? Anyone heard a good fix? Or did they have a bad batch of batteries? I heard duncan replaced 4 batteris durnig that 12 hours in france race before they figured running the lights on helps!

 

Okay Ridley, so what is it that they changed? I called Duncan Racing and asked them how they were fixing the problem, and they said it was an issue dealing with when the fan kicked on. they said that even if you have the headlights off, leave the switch on and retail your stock starter switch on your handlebar and that will solve any problems. Sounds okay, but what if "oops" I bump it off during a race. Do you by chance know what yamaha was doing or what was causing the problem?

 

The YFZ uses a series regulator/rectifier which by design is not high quality. As I recall, the battery is on the DC side of the system so removing the battery and keeping the fan is not possible unless you add a big capacitor to replace the battery.

I have measured four YFZ's and none of them were putting out too much voltage for the stock battery. As for the "turn the lights on" theory, this makes no sense. All the "lights-on" solution will do is draw the voltage down if the regulator/rectifier is not working. When you rev the motor or turn your lights off, the voltage will just run high again and toast your battery. At best, "turn your lights on" is a band-aid.

If the battery is charged and the regulator/rectifier is keeping the voltage at 14.3VDC then the battery will push back on the system and not accept over-charging.

If you suspect your YFZ has problems, the test is simple. Put a voltmeter on the battery when the quad is off - it should be near 12 volts. Start the quad and the voltage should run no higher than ~14.3 volts. If you see voltages in the high 14's or above, you have a bad regulator/rectifer. The best regualtor/rectifier to use is a full wave (clean power).

If you make this check and find low voltage then you likely have a spent battery. Replace the battery and run the check again, if the voltage is correct, your problems will be gone.

 

That's exactly what I was looking for thor! I ended up calling trail tech last night and that is the same advice they gave me. Just gotta get home now and borrow my buddy's meter to get it all checked out!