CB750SC nighthawk not charging...enough that is

[Out]

Got a buddies 82 nighthawk 750 to do a few things on. New battery in - chain, sprockets, brakes and F master on the way. It has a new Rotor Stator, and RR installed from the PO. I rode it a week and it is not charging enough. Rev it and the lights brighten, but no volts over 12.5-8. I followed all the stator/rotor diagnostics, Ohm'd items per the book, cleaned the brushes/rotor face, cleaned all contacts from the main fuse to the ignition switch and it still charges low. I jumped the ground to the reg/rec and it charged up to 13.8. I am guessing the RR is bad but dont know for sure. Can the little stack of fuses have any bearing on charging? I saw a thread on replacing them with a blade fuse. I checked all power and grounds with a spare headlamp to verify good juice. I have a new reg/rec coming just to rule that out as it fits my other Honda DOHC"S. Looking for thoughts while I wait on the reg...guaranteed delivery was yesterday?!?

 

[teazer]

You can check the AC voltage to see if it rises to where it should be when the motor is revved up.

Is it a permanent magnet alternator or electro-magnetic type ? Make sure it has the right type of regulator as the two types are different. With an electromagnetic type, it is essential that teh field coil gets a full 12v so check the lead that powers the field coil.

 

[pidjones]

If grounding the sense lead to the regulator causes it to charge full, then I would suggest a regulator problem. Yes, check the voltage to the field coils, but I suspect it only goes to 12V when you ground the sense lead. Once the battery is topped off it should vary to maintain the output at around 13.8-14.8V

 

[cxman]

check the rotor that is usually what it is

that 82 nighthawk is a 750 dohc with another name

just google dohc charging issues you will find it all

 

[Out]

You can check the AC voltage to see if it rises to where it should be when the motor is revved up.

Is it a permanent magnet alternator or electro-magnetic type ? Make sure it has the right type of regulator as the two types are different. With an electromagnetic type, it is essential that teh field coil gets a full 12v so check the lead that powers the field coil.

It varies the current/voltage to a field coil to increase charge. The change is on the ground side I believe. I have a good solid 12V in - enough to run an old tractor headlight as that is my "load tester".

 

[Out]

If grounding the sense lead to the regulator causes it to charge full, then I would suggest a regulator problem. Yes, check the voltage to the field coils, but I suspect it only goes to 12V when you ground the sense lead. Once the battery is topped off it should vary to maintain the output at around 13.8-14.8V

That is what I am hoping. I have never had good luck testing reg/rec's. When I can a known good unit comes off the shelf or another bike. The one I ordered should be in Sat so fingers crossed!

 

[Out]

Work is 4.3 miles so not charging is OK for that on a nice day!

 

[Out]

Fixed!. The new reg/rec came in today so I popped it on, and low and behold the old one had a crack and a raised bump leading from the crack into the backing material. Fired up and was at 13.8 at 2500.

 

[Out]

View attachment IMG_0961.JPG

 

[Maritime]

thats a good deal.