Topic: '76 CB550 vs. '79 CB650

[TwoTired]

I agree 20 V might damage the rotor.  I have a hard time believing the battery could be overcharged (and survive) to 20V.  The scenario makes more sense if the battery boiled out and became open circuit.    Then a failed regulator (fused to it's input, rather than open circuit) could cause the scenario described, I suppose.  But, normally the battery will buffer overcharge for quite some time.  It might also be that the battery failure cause the regulator to fail, etc.

But, damn, that's a lot to go wrong all at once.  What are the odds?

It IS important to check the electrolyte levels periodically. 

Anyway, it just seems more likely that motor heat, errant oil, and centrifugal force are more likely to fatigue the winding insulation and cause it to short out.  But, what do I know, I've rarely ever seen a Cb650, let alone worked on one.

Ride safe.

[Pinhead]

I agree 20 V might damage the rotor.  I have a hard time believing the battery could be overcharged (and survive) to 20V. 

The battery  most certainly didn't survive.  

The scenario makes more sense if the battery boiled out and became open circuit.    Then a failed regulator (fused to it's input, rather than open circuit) could cause the scenario described, I suppose.  But, normally the battery will buffer overcharge for quite some time.  It might also be that the battery failure cause the regulator to fail, etc.

But, damn, that's a lot to go wrong all at once.  What are the odds?

It's only 1 thing that went wrong that caused the rest... Apparently happens pretty often, as this seems to be the death of many a 650.

It IS important to check the electrolyte levels periodically. 

If I knew then what I know now.

Anyway, it just seems more likely that motor heat, errant oil, and centrifugal force are more likely to fatigue the winding insulation and cause it to short out.  But, what do I know, I've rarely ever seen a Cb650, let alone worked on one.

I've never actually seen oil in the alternator housing, though there is an o-ringed bung at the bottom that I suppose could fail, allowing oil to enter the housing. I suppose a crank main seal could go out as well, causing the above scenario.

I suppose it could go the other way, too... The rotor shorts out which takes the regulator with it. However, most of the R/R's that I've seen had both the regulator burned AND at least 1 leg of the rectifier fried. The bad rectifier would further point to an over-voltage situation.