Hi! First of all I'm not a very avid forum user I have searched to try and make sure I'm not going over old ground but I may have missed an earlier post so please be tolerant! Bike is an XT600Z 3AJ. Battery not charging properly, charging just enough with no lights on but as soon as lights or indicators on battery is discharging. I've measured continuity between three white wires from stators resistance between any two of the three about 2 ohms. No short between white wires and ground. With bike running at tickover
I get about 10 V AC between two out of the three wires and 25 V on the third. On revving up the lower readings go up to about 18 and the higher rises to 45. I had thought that the difference meant there was a stator fault but now I see from an earlier post that on the AJ one coil winding is different and used for ignition: Is this what I am seeing or maybe not cos how would bike be running at all with the regulator/stator connector open if that were the case?
So, does the values of AC I've measured mean I have a problem inside the stator?

I tried to then measure output of rectifier/regulator but bike will only run with blue/red two pole connector from regulator connected and then all I see is voltage pulled down to battery voltage.

Sorry if this is a daft post but I need to know what to do next and if the problem is the stator am I best getting it rewound? Any suggestions as to a good supplier?

Thanks for your help guys

You should get the same reading on all three yellow(or white) wires when measuring between any two . The ignition is the other wires coming out of the stator . Sounds like you have a bad stator.






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I have also a charge problem, have not messured any voltage or resistance of the stator wires, but the bike started to feel low in power, like its not getting fuel last ride in fall. I did check every fuel related problem, and ended up messuring voltage at the battery, and at idle it had ~13 volts, and as rpm ride the voltage drop, eventually below 12 volts at high rpm! So I did not have time to do ant to it then, and did just bring it home from winter storage last weekend. Talked to a local shop, that is a approved Yamaha service place, and the mechanics there has several years of experiance of working on Yamahas, actually Yamahas importer use them for the big and nasty jobs the importer can´t deal whit! Anyway he did simply say my stator is bad, and reason is the old stators lacquer just can´t stand the ethanol in todays fuel, as part of it eventually go down in the engine oil, and as the lacquer let oil past the stator shortcuts. And the higher the frequency (=higher rpm) the easily the shortcut occur, and voltage drops. So I will first take the stator from the other engine and see if it works, if not, I guess I just have to get myself a new stator!

Hi,
this would also be a standard indication for a bad battery. So maybe first check behaviour with a replavement or a battery from another vehicle.

Extra test: when revving and the voltage drops, use the horn or make the brake light shine, and that should INCREASE the voltage reading - then it is most probably the battery.
Or when you ride, at some point the flasher relais will not work because the voltage is too low. But it would work while braking or pushing the horn button. Same thing - bad battery.

Andy
still on the first alternator, regulator and CDI for 30 years

keny72 wrote: and ended up messuring voltage at the battery, and at idle it had ~13 volts, and as rpm ride the voltage drop, eventually below 12 volts at high rpm!

I had the same symptoms on a 3AJ, voltage getting lower on high rpm's or longer rides and that was over after I installed a new regulator/rectifier.

Had the same issue on a '91 XJ600 which uses the same regulator : voltage would go down on longer rides... got a new rectifier from Aliexpress and the problem was gone.

Also make sure the Reg/rect. housing is grounded good to the frame and battery . I run a dedicated wire from the frame (and another wire from the frame bolt to the battery)to one of the mounting bolts to makes sure it had a solid ground. Can't get too good of a ground.


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I did look at the battery, as I did take it from the winter storage it was a bit dry, had to add some water, and now even I have charge it for several days it looks it will not take full charge.....so a new battery first. The look at the R/R as a dry battery seem like it gharge to much.........