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Discussion Starter #1
Ok guys, I rode about a hundred miles the other and came in to work. When I left work the battery was too low to start the bike and I'm too fat to push start it.

I towed it home and started poking around a little. Battery voltage was about 11.5 key off, falling to 10.6 as soon as I turned on the key. Now the battery is only about 14 months old and I keep a tender on it when I'm not riding so I suspect that is not really the root cause of the problem. I charged the battery until my tender said it was fully charged and checked the voltage again.

I had about 12.6v with the key off. Turning the key on dropped it to about 12.2v. I started it up and checked voltage again. At idle I had just under 12.3 volts. Giving it a little bit of throttle it did raise some, but only just, getting up to all of 12.5v.

I would have expected 13+. Obviously I've got a charging problem, the question is where? The bike is a 2004 with 44k miles on it. I will of course double check all of my connections to make sure they are clean and corrosion free. Beyond that my first suspect is the stator. I certainly don't mind to replace it, but I would like to be able to definitively prove that the stator is bad first.
 

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My first move would be to take the battery somewhere and have it checked. That is a no-cost deal, besides the work and inconvenience. If the battery tests good, including a load test, you have to look further. The battery is also (probably) the least expensive replacement.
 

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Ok guys, I rode about a hundred miles the other and came in to work. When I left work the battery was too low to start the bike and I'm too fat to push start it.

I towed it home and started poking around a little. Battery voltage was about 11.5 key off, falling to 10.6 as soon as I turned on the key. Now the battery is only about 14 months old and I keep a tender on it when I'm not riding so I suspect that is not really the root cause of the problem. I charged the battery until my tender said it was fully charged and checked the voltage again.

I had about 12.6v with the key off. Turning the key on dropped it to about 12.2v. I started it up and checked voltage again. At idle I had just under 12.3 volts. Giving it a little bit of throttle it did raise some, but only just, getting up to all of 12.5v.

I would have expected 13+. Obviously I've got a charging problem, the question is where? The bike is a 2004 with 44k miles on it. I will of course double check all of my connections to make sure they are clean and corrosion free. Beyond that my first suspect is the stator. I certainly don't mind to replace it, but I would like to be able to definitively prove that the stator is bad first.
under the fuel tank to left side of the rear coil there's 3 pin white plug, pull the plug apart and ohms test on the stator side from the center pin to left and right pins reading should be 0.50-0.62 ohms x 100s then test all pins to ground there should be no continuity should be an open. take the reading @ 68 degrees or better. the only specs for the regulator are 18 amps with a 200 withstand volts
 

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Discussion Starter #4
The 0.5 - 0.62 ohms is in the service manual. I tested mine and it read 0.8 ohms. Now my garage is colder than the 20 degrees C they recommend testing it at but since cold tends to decrease resistance rather than add to it, I would say it is safe to say it is out of spec.

Yamaha does not specify checking the resistance to ground but you are the second person who told me there should be no continuity so I checked that. I checked resistance to ground from all of the terminals and got 1 ohm on all of them, so this is a second indicator that the stator is bad.

I also checked AC voltage directly from each of the stator terminals to ground. I got about 8 volts at idle and with a little throttle they leveled off at 11.8 volts. I couldn't really find a specification for this. 11.8 volts RMS would be close to 16VDC so that actually seems like it might be ok but with no specification to compare it to, this test really doesn't tell me anything.

Guess I'll be looking into a stator now! At least it was time to change the oil anyway.
 

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Make sure to check the wire harness from that connector all the way back to wherever it enters the engine. It is possible for the wires to have rubbed against something and shorted to ground. I had a Suzuki on which the stator appeared bad, but the problem turned out to be the wire harness rubbed against the chain and wore through.

Also, when checking the stator output voltage you do not check from the wires to ground. You check between pairs of wires. What comes out of the stator is three-phase AC on three wires, and it is not ground referenced. That check is done with the stator disconnected from the voltage regulator, and while your bike might be different you should be seeing several tens of AC volts from any wire to any other.
 

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Discussion Starter #6
I'll check it out.

I know Electrosport seems to have a bad name but they have a pretty comprehensive troubleshooting guide. They give a spec for phase to phase voltage on the stator and it's supposed to be over 50. I'll definitely check that out but I have a feeling I won't get much.
 

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I'll check it out.

I know Electrosport seems to have a bad name but they have a pretty comprehensive troubleshooting guide. They give a spec for phase to phase voltage on the stator and it's supposed to be over 50. I'll definitely check that out but I have a feeling I won't get much.
check the stator for grounds at the white plug with three white wires under the tank left of the rear coil if that test good and it tests bad at the regulator you'll know the stator's good and the 2nd harness to the regulator is shorted to ground. i doubt the 1st harness grounded as it's better protected behind the engine. road debri and wind can get to 2nd harness. connect a test light to batt positive and probe the plug which ever pin lights it, that set of coils burned and grounded on the stator.
 

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Discussion Starter #8
The stator shows continuity to ground at the actual stator harness with nothing else connected. I haven't dug into it to see if it is shorted from the plug to where it goes into the engine but I bet I won't find anything there. My guess is it is internal.

To be fair though I really can't complain too bad. It's got 44k miles on it, the crank pickup failed last year and I replaced it independent of the stator because I really didn't want to pay for it at the time. In retrospect maybe I should have replaced the stator at the same time :p
 

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The stator shows continuity to ground at the actual stator harness with nothing else connected. I haven't dug into it to see if it is shorted from the plug to where it goes into the engine but I bet I won't find anything there. My guess is it is internal.

To be fair though I really can't complain too bad. It's got 44k miles on it, the crank pickup failed last year and I replaced it independent of the stator because I really didn't want to pay for it at the time. In retrospect maybe I should have replaced the stator at the same time :p
when i did my pickup i released the pins from the plug to push em through through the grommets so i wouldn't have to splice it. one thing i learned about the pickup is not to reverse the wires when putting the pins back which is easy because their the same color
 
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