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79 DOHC charging problem???

Hippie459MN

CB750 Addict
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Saint Francis, MN
So about 2 years ago my bike suffered from a dead battery while out riding one day and turns out the rotor went south and I ended up replacing it. I will admit, I have not tested the regulator/rectifier at all so that will be my starting point here soon I think. The problem is, since replacing the rotor, I am getting 14v at the battery with the bike running but the issue is, I dont think its putting out the amperage it should cause I will charge my battery and for a few weeks it will start great and run really good then eventually it will not want to start, flood easy when on a cold start, but once its running, it runs ok. But if again put the battery on the charger for a while, it will again start up perfect and super easy, and run just fine. The battery was replaced about a year ago but even did it with a brand new battery. My bike only has a headlight and a tail light (l.e.d.) so I know other than the ignition system there is no big draw on the battery. I guess what my question is, is there any way to test the amperage output of the charging system? I know the voltage is there but I dont think its putting out enough amperage to keep up with the draw. And could that be a regulator/rectifier issue or would that be more of a rotor/stator issue? I have just gotten use to throwing the bike on the charger after I go riding but would like to not have to do that all the time.

Sorry for the long winded post. lol Thanks.
 
Ok, I checked the 3 yellow wires off the stator and all came back about .7 on the 200 ohm scale on my multi meter I have and none of them show an open ground so assuming that is good. Might have to track down an amp meter though to test the amp output. Going to look into the regulator/rectifier next. Seeing that they say if the rotor goes south that usually goes with it and I never replaced it. At least I have a month or two yet before any decent riding weather.
 
Don't overlook repeat rotor failures and it's common. The rotor being the weak link on the DOHC charging system. And they can fail in multiple ways too. The people that make or rebuild them have fits with them as well. The rotor can even test as good over and over and still be bad, bad, bad.
 
It was a brand new Ricks Motorsports rotor and I have had this issue since putting it in and its only 2 years old now. I wouldnt imagine I would have a bad new one right off the bat or it going bad so fast.
 
Nor do others but it happens. The OEM one glues the windings all the way down to the core, I do not specifically know about Rick's but common for others to only glue the outside of windings down and that is shortlived. The entire core has to be solid glued or the wires at centrifugal speeds abrade each other to short out part of the coil and then reduced charging that can be rpm related. Meaning it will test as good all day long until you spin it fast enough to short.

I've had the OEM rotor fail 2 months after getting brand new bike....................
 
I will have to look into this further. I guess if it comes down to it, I just replace everything. Rotor, stator, and regulator/rectifier. If I still have issues then, blow it up... haha
 
Yours and do as you will.

I never change the stator myself and regulator rarely. Rotors? Oh yeah..........the reg goes when owner insists on pushing a bad rotor too long. The reg then overheats from trying to pump up the field because the rotor is not properly outputting due to shorted windings.

The problem is that a spinning field fails MUCH faster than one that does not spin. The DOHC adds to that by locking the alt up inside an airtight hole that gets ZERO cooling air, making the epoxy crack super fast.
 
Yours and do as you will.

I never change the stator myself and regulator rarely. Rotors? Oh yeah..........the reg goes when owner insists on pushing a bad rotor too long. The reg then overheats from trying to pump up the field because the rotor is not properly outputting due to shorted windings.

The problem is that a spinning field fails MUCH faster than one that does not spin. The DOHC adds to that by locking the alt up inside an airtight hole that gets ZERO cooling air, making the epoxy crack super fast.

http://www.motorcycleproject.com/text/DOHC_charge.swf
 
The stator did check out good so will prob leave that. Im going to check out the rotor again and check out the regulator/rectifier. I dont have the best digital multimeter so we'll see. lol I report back with my findings sometime today im sure. Thanks. :)
 
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