Charging woes, 79k

[alehman]

So I know what my problem is here-- my rectifier regulator went bad. I just don't know WHY it went bad, and I should probably figure that out because it's only a few months old. I want to know for certain that it's not some problem with my rotor or stator that will cause another R/R to go bad.

Here's the background: I had another CB750 I was trying to get running and its rectifier/regulator went bad, so I bought this new one and had it on that bike for a while. I recently bought a running CB750 and replaced its R/R with the new unit I'd bought, figuring it was working. A month and a few drained batteries later on the new bike, I tested and figured out that the new unit is dead.

I wanted to get your guys' expertise on whether or not it was my non-running cb750 that toasted the R/R or if it could have been my new bike.

Reason why the new bike could have been the cause: the rotor and stator test as having higher than specified resistance; however, there are no opens. Reason why the old bike could have been the cause: with that old bike I was constantly deep-cycling the battery trying to start it up, and I've read that that could cause an R/R to go bad, don't know why though. Also, the original R/R--- which was only ever on my old CB--- and the new unit failed in the exact same way according to my multimeter.

[Hellbilly429]

How much higher resistance are they testing? Did you test multiple spots around the rings on the rotor? you will probably find inconsistencies that will prove the rotor is shot, and they can go bad without any warning.

[alehman]

here are my readings:

there is a factory specified resistance between the 3 yellow terminals of the stator, which is .41-.51 ohms.
mine are exactly 2.0 between the 3.

for each of the stator's total 5 terminals, there should be no continuity with the ground, and mine have none.

For the rotor, there is no factory-specified resistance between the rings, but my clymers says there should be some-- "approximately .4-.5 ohms." Testing multiple points on each ring, I consistently got 5.5 ohms. Neither ring had continuity with the ground, either. No opens.

[Hellbilly429]

Here, watch these videos and you will get a better understanding of the issue. Sounds like the stator is bad, but the rotor sounds like it is within the acceptable range of ohms. I do not understand why the clymer manual says the rotor should be within .4-.5 ohms, but I think it was a typo as you will see in the 3rd video (I believe) that a new Honda OEM rotor should read more than 4 ohms.

[alehman]

Thanks Hellbilly, those videos are pretty good. Luckily, in the second one he says that as long as there's continuity between the terminals of the stator, it doesn't really matter what the resistance is, so it's probably not the stator.  also, this isn't the first time the clymer has been wrong about certain facts.... a little ominous. Luckily my new R/R had a year warrantee and I should get a replacement soon.

For now I'm going to rest confident that it was something about the old bike that messed the R/Rs...