Stator checks out on continuity test.

Rotor is good, although the resistance across the bands might be a little high at around 6 ohms. But it did come that way back from the guy who rebuilt it last year and he said that was ok. I was charging with over 14 volts when I first put it in last year.

The diodes on the rectifier all check good.

Brushes are in good shape.

The manual says "disconnect the stator six pole connector. Connect an AV voltmeter leads to any two Y wire leads." So I put each probe on one of the Y wires and switched to check them all 3 combinations. I'm reading 0 volts from that test at idle. Not sure if I did it right or not. If I connect the stator connector back up and read each of the yellows with the black probe on a ground I read 13.0 volts across all three. When I rev the engine I read 14.6 AC volts on all three.

I also has some strange behavior with the cheap $50 napa batter I have. First of all, the one I got last year went bad in less than a year. I warrantied it 3 weeks ago. With the new battery in I was charging at around 13.7-14 volts, but only after the rpms were held at 3000 for maybe 20 seconds. Yes I use a trickle charger before using my batteries.

It seems to me like the stator is the likely culprit. I think I'm also going to run that battery up and have them check it. I'll update with the results of that test in a little bit. Any thoughts on the likely problem?

 

My vote WOULD BE the stator... do you happen to have any burned looking wires in that area... specially around a connector joint?

 

If it is burned It doesn't look that bad, but I've never had a bad stator so I don't know.

 

I've already checked and cleaned all connections. I did the stator test again, except this time I left the 6 pin connected hooked up. The manual says to disconnect. I read about 9.7 ac volts for all 3 combinations of those three wires which is within the 8-10 ac volts the tests specifies for it being disconnected.

I read that a rotor failure which happened to me last year can cause the regulator rectifier to fail. There is no way to test the regulator, so maybe that's bad. I had a bad delco cs144 alternator on my jeep that had the same charging characteristics as this bike and it was the regulator. I've always heard that stators rarely go bad and looking at these pictures I'm not convinced.

Here's a link to the manual if anyone is interested.
http://www.cb750c.com/publicdocs/

 

I had similar issues to what you are describing and it was crappy wiring out of the Stator, they checked out fine on tests, but during operation due to vibration they would sometimes become "disconected". Check the wiring for kinks, etc.

 

Got a used R/R off ebay. Either that wasn't my problem, or the one I got was bad as well. I pulled the stator out and those wires look fine. Battery is also fine. I took the battery out of my dad's harley and I wasn't able to charge with it either.

I overlooked this, because I didn't think much of it at first, but I'm starting to think that this is my problem. On the rotor, it doesn't look like I'm getting an even contact from the outer brush. Do you guys think this might be my problem? The thing that I don't understand is why if this is the problem did the bike charge at over 14v when I put the new rotor in if the brushes did not have good contact? I never replaced the brushes at the time. The brushes look nearly brand new.

For $17 from Rick's electric, I think I'll give it a try. Hopefully they aren't junk. The Honda shop wants about $65 for a pair.


The rust on that bolt is from me forgetting it outside when I was waiting for the rebuilt rotor. There is no water entering the case.

 

Yup, I think that was the problem. I thought it was a problem because the mark wasn't even on the slip ring. Apparently the brushes aren't suppose to leave marks like that at all. I'm going to clean up the rings with some contact cleaner and a scotch-brite pad and get new brushes. I'll update in a few days to confirm if that fixes everything or not.