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Replaced Rotor and regulator, still no charge

rs_ss350

CB750 Enthusiast
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oakland, ca
So brand new regulator/rectifier and a brand new rotor. Old rotor tested bad, new one tests good. The stator tests good, but seriously it could be the only thing that's the problem since I replaced the other two items, right? Just need a second opinion before I keep dropping more cash...
 
4.6 ohms... i've gone ahead and ordered the stator in defeat... if this doesn't work i'm going to go nuts. a wise man told me to check the grounds... do you know the locations I need to check?
 
Stator if tested right should be pretty reliable.

A ground to frame for various parts including regulator and battery has one as well. If 750 solid mounts and they ground to frame too.

The rotors can be broken winding inside and test OK since touching then, then you spin them up and centrifugal force then separates broken wires or shorts them out. They at that time will then check as good again. I had one once that measured perfect but it was bad in the long run. Of course I did just like you here but didn't buy a stator, it tested fine. If rotor is a rebuild (they almost all are) then suspect it, many are crap.

Like Ford modern 6G alternators, they commonly test good too and are bad bad bad. The diodes fracture the connections then they test fine until you use alt then the heat and vibration makes them vibrate diode leads to be in the middle of contact/no contact. They can be failing months before you get actual running issues. Yet will pass test after test at idle.
 
I bought a Rick's Rotor, i'd heard they were reputable. Actually now that I rechecked the rotor I removed, that one tests good too! And a I look at the components, it looks like maybe the previoud owner had aready gone through and replaced most if not all of the parts already. Perhaps why previous exasperated owner got rid of it without divulging the issue. Anyway, what're the chances of having two bad rotors that test good? How can I prove it in order to return the one I just bought?

on the issue of the stator... i got a new one (Rick's) and might just want install it to at least rule it out. but i'm finding the routing of the wire to be troublesome... it's a tight squeeze getting the connector thrugh between the engine and the frame towards the rear of the engine... any tips on that are much appreciated.
 
OK, so I got the new stator, replaced the brushes while I was there... the new statro from ricks, it seems a bit thicker - see the image below the stator surface is not flush to the mounting surface - see the space between the screw and the cap. Is this OK??

Thanks!

IMG_0198.jpg
 
OK, so put everything back together... still no joy. So i called the local bike mechainc and he gave me another test. He says that with the ignition on (not running), the rotor should become an electromagnet with a significant pull. There is some magnetism when i check but nothing too strong and it seems the same whether the ignition is on or off... is this guy pulling my leg?
 
OK more questions... keep reading that a bad rotor will fry a good regulator/rectifier... so my first swap was the r/r. that didn't fix it, but the question is, will just running it for a little bit (10 mins) be enough to "fry" it with a bad rotor? feels like i'm going in circles and i'd just really love to ride this bike already.
 
If something fried you can do a regulator in instantly, depends on the problem. 50 different ways a rotor can short. Engine is usually idling to do a case magnetic pull test. It really doesn't tell you a whole lot. Can't do it with ignition off, that would be running battery down and a symptom of blown diode in regulator. I would be pulling stator to check for trash under it at the ring where it seats, if no then do what it takes to shim those screws tight, otherwise they WILL come loose. You can't expect a screw half on something to stay that way. I'd most likely be making some washers up of correct thickness then grinding part off to make a like 2/3 washer OD rather than all the way around then carefully locate to make the screws then tightening down both stator AND against the aluminum of the case. Last forever if done right.

Rick's is not above putting out a bad part or two, I've heard of it.

Take both rotors, clean the brush tracks and then measure ohms. Track to track. Then each track to the steel hub where the bolt goes through. That last measurement should be infinity as in no power; it would be a rotor short.

The stator harness is normally taken off engine after engine is yanked for the reason you mentioned. can't get it out engine in frame.
 
Don't remember if we've been there or not but if you do not have a KNOWN GOOD FULLY CHARGED battery you are wasting your time here. Alt field (your case magnetism) depends 100% on the condition of the battery. The alts will NOT charge even if good with a less than sufficient battery.
 
I bought a load tester and checked both of the batteries I have (one brand new and another that was on the bike when i bought it - suspected also new) and they both check out like this - while close to the weak area, the troubleshooter here (http://www.motorcycleproject.com/text/DOHC_charge.swf) says anything above 9.5v under load is good, and this is giving me close to 11v.

IMG_0352.jpg

been through lots of troubleshooters on lots of sites. this one points me to the stator, but it's awfully hard to believe that i'd have replaced a bad stator with another bad stator. i'm so frustrated by this issue...
 
Dunno what to say other than 100% of my few errors were all rotors. A brush lead broke once. The stator can fail of course but they should be super simple to check for flaws that make them do so. The only part you really can't test is the regulator, and you can even check the diode section of it.

After many years of working on cars and bikes and even the PCM controlled stuff with no formal training at all, all I can say is that you have probably just missed something since I have never seen a car or other that I eventually couldn't fix to run perfectly. When you get to the end of all work and it's still not right then obviously something was missed and it often points directly at the caliber of your work. Not trying to insult at all, I do the same to myself and how I come up with the new angle that fixes something I couldn't before. I NEVER run out of a backup or backup of the backup plan.

I do understand alts, I rebuild the PCM controlled ones on my Fords all day long, they are utter crap design and often I can resolder a simple diode contact to have one up and working again for pennies instead of buying them at $200+ apiece.

If you are pointed at stator then check it again. Reinforce your thinking that it is good or bad, there is no in between. 3 simple loops of wire, they all have a certain resistance in each and each attaches at one of its' ends to the other two to make essentially a Y with the outer loose ends giving power to the system. The Y cannot ground anywhere.
 
Looks like it was the (new) rotor after all. The new one i had was testing at 5+ ohms... maybe the resistance was too high. Got a rebuilt one from Rick's and it tested at 3.5 ohms, and now the system is charging. thanks for helping!
 
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