81 cb750 charging issues

[ngeiling84]

Ok I have an 81 cb750 k and im stumped. I have installed a new generator rotor, the alternator/stator ring checks good and the brushes check good but while the bike is idling its only charging at 12.78 volts. Is there a way to check the regulator/rectifier or does anyone know of something I'm missing...... Please help

 

[mydlyfkryzis]

I doubt it charges at an idle. My 1991 CB750 just keeps even at idle (12.7 Volts)....Full output isn;t available until 2500 RPM or higher.

Does the voltage climb if you hold 2000 RPM?

 

[notlob]

Yep it doesn't kick in charging until 1700rpm and will rise to approx 14.8V If it keeps rising above 14.8V your regulator is probably faulty

 

[ngeiling84]

It stays the same doesn't rise at all, I don't have a tac so can't be completely sure. I revved it up pretty high but I will try again tomorrow and post my findings. Thanks for the help guys

 

[hillsy]

There should be a proceedure in the manual to check the regulator/rectifier.

Sounds like this is your problem (could be bad wiring connections / earthing).

 

[ngeiling84]

Ok guys another question, I have not tested the rectifier still I know I should have and I'm sorry but I noticed that from what I have looked at that the generator rotor is touching the stator ring, from what I know that would affect the charging am I correct everything I have tested checks ok still.

 

[Hoosier Daddy]

Good rule of thumb in mechanics is anything rotating (rotor) should not touch anything stationary (stator).


But for troubleshooting purposes on your DOHC CB the the factory service manual for a CB1000 and recommended as the best info and I posted a link in the "Shop and Parts Manuals" section here on DTT.

http://www.cb750c.com/publicdocs/CB1000C_Manual/Chapter_18_Battery_and_Charging_System.pdf