Topic: Cb650 electrical system won't charge

[nate sere]

I have a Cb650 which will only run about 3 or 4 days before the battery dies.  I just tested it and it's getting 12.7 volts at idle, and it goes up to maybe 12.9 at full throttle.    I changed out my regular rectifier with another one and it didn't change anything.   What should I check next?

[onepieceatatime]

You should check the rotor and stator.
Rotor resistance should be 4-10 Ohms between sliprings, no contact to ground/rotor chassis.
Stator resistance should be 0.4-0.5 Ohms, symmetrical between each pair of yellow wires, no contact to ground/stator mounts.

[Mainerider]

The voltage regulator is usually not the issue with your model bike; much more often it is the rotor. BUT, before you continue to just guess at the problem and waste additional money you really should do some basic electrical diagnostics first.  Are the battery cables in good shape, with clean connections,  and on tightly?  That includes the ground end of the negative cable. Is your battery verfiably good?

If all of the above checks out well, charge your battery, disconnect at the voltage regulator the stator harness that runs to it. There will be three yellow AC wires in the harness.  With the bike running, test all three for AC voltage with a multimeter. All three should indicate roughly the same amount of AC voltage. If memory serves, you should see approximately 78 volts on each lead.  If a lot lower, or no voltage at all on any of the three leads, you've found the problem.

With the bike OFF, you can also test the stator for continuity; set your multimeter to ohms Rx1, and test these same three yellow leads for continuity amongst each other.  You should have continuity between all of them.  If the stator fails this test, the stator and not the rotor is the likely culprit.  But as I said earlier, the rotor is the problem more often that the stator.

[nate sere]

I am at .5 ohms at the slipring on the rotor.

[nate sere]

Stator resistance is .5 across all 3 wires.   

[fmctm1sw]

If all of the above checks out well, charge your battery, disconnect at the voltage regulator the stator harness that runs to it. There will be three yellow AC wires in the harness.  With the bike running, test all three for AC voltage with a multimeter. All three should indicate roughly the same amount of AC voltage. If memory serves, you should see approximately 78 volts on each lead.  If a lot lower, or no voltage at all on any of the three leads, you've found the problem.

That's how I found a problem with a friend's Rebel...  I think it was around 50-60 volts/ea though IIRC..  There is a electrical troubleshooting PDF somewhere that I used to help me.  I'll see if I can find it.   here:  http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf  Something tells me I never would have tested my regulator though.  I may have been confused by the letters...

[nate sere]

With the bike running and voltage regular connected, I have 4 volts ac on each yellow wire and ground.    With it running and disconnected, there is no voltage. 

[fmctm1sw]

With the bike running and voltage regular connected, I have 4 volts ac on each yellow wire and ground.    With it running and disconnected, there is no voltage.

If you disconnect all three yellow wires, I don't believe the regulator ever has a chance to work regardless.  I think you take the reading between the yellow wires, not wire/ground.

[nate sere]

Connected, yellow to yellow it reads 0 volts ac.   Disconnected it reads 0 as well.   

[nate sere]

The brushes on the rotor are in great shape.   

[Mainerider]

it sounds like it's time to pull the stator  cover off.You're not producing ac voltage and the rotor is usually the issue on these bikes.Do you know the testing procedure for the rotor? If it is the rotor you will need a flywheel puller to remove it .You can Mickey Mouse it by using your axle bolt as a puller but a proper puller isn't much money.  Can't remember the size but will check when I get home.

[nate sere]

What is the testing process for the rotor?   Different from what I've already done?

[Mainerider]

Sorry; hard to follow the posts clearly on my CrackBerry. Its hard to diagnose completely accurately sight unseen over the Web but it does sound as though your rotor is the culprit. is it still on the bike?

[Mainerider]

By the way, I just replaced a rotor on a friend's '81 650;Do you want the puller size that we used?

[TwoTired]

I am at .5 ohms at the slipring on the rotor.

You found the problem.  The rotor is bad. 
I'll warn that with rotor resistance that low, it can cause the regulator to fail too, as it forces the regulator to pass 25 amps instead of 2.5 Amps.
Your new regulator may not have survived.  10 times loading usually breaks things.

[curemode2002]

TT is right that rotor resistance is way to low. To be sure pull the stator cover and go from ring to ring and measure the resistance on my rebuilt rotor I was getting 5.3 Ohms for the CB650 4.2-5.6 is the sweet spot. I would recommend the Regulator/Rectifier testing that fmctm1sw mentioned above that will tell you if your RR is dead.

Also a great guy to rebuild your rotor can be found at http://stores.ebay.com/Tim-Parrott-Enterprizes?_trksid=p4340.l2563
This guy does awesome work for a good price and he stands behind his work longer than any aftermarket rotors I have found.

Another thing I found with my rotor issues is that your stator brushes need to be replaced as they get overheated trying to push the extra juice that TT mentioned above. They can be found just about anywhere but z1enterprises.com has them for pretty good prices.

[Mainerider]

I just double-checked using my spare rotor; The puller is a 18mm x 1.5 RH thread.  Nice to have a complete, low-mileage disassembled spare parts bike in the basement...

[trueblue]

I am at .5 ohms at the slipring on the rotor.

You found the problem.  The rotor is bad. 
I'll warn that with rotor resistance that low, it can cause the regulator to fail too, as it forces the regulator to pass 25 amps instead of 2.5 Amps.
Your new regulator may not have survived.  10 times loading usually breaks things.

+1 I had this exact thing happen to my bike, the rotor died and killed the reg/rec.