Topic: CB550F not charging

[Rick Vessell]

77 CB550F.  Bike starts and runs great after my recent carb rebuild and cleaning.  Bike is not charging however.  I was riding pretty regularly until recently when it quit charging.  I installed a combo reg/rec unit shortly after I bough it last year when the factory reg went poof.  I have also replaced the fuse block with the blade type due the famous melting terminals.

Here's what has me frustrated,

When I check all components per the info in the FAQ here, everything checks out according to spec.  Field coil is within spec.  Each leg of the stator is within spec.  Voltage on the reg leads as should be with key on.  When running, no output from stator, zero, not even low voltage.  I checked all leads and interconnect wiring for shorts and opens also.

So, is my stator shot?  I pulled it and it does not appear or smell burnt.  Neither does the field coil.   

[TwoTired]

Do you know the stator produces AC power?  it's not DC until after the rectifier.  Multimeters use different setting for these measurements.

If you are measuring correctly, what voltage appears on the field coil (DC) when you desire the stator to produce AC?

Rather rare for the stator to go bad, unless there has been some physical trauma.

[Rick Vessell]

Yes, I know the stator output voltage is AC to the rectifier.  I had the meter set for AC when I was checking it.  Did not think to check the field coil while running, just did the resistance check with it.

What should I see for voltage at the field coil leads when running?  I didn't think stators went bad either honestly.  Is it possible I have a bad field coil?  That seems rare also.

[TwoTired]

I've had a field coil go low resistance, which weakens the magnetic field.
The field coil gets battery voltage when the vreg senses the battery is low.  So, usually at idle speed, expect to see battery voltage on the field coil leads.  When the battery is filled (over 14.5V), the field coil voltage can be zero.  The field coil voltage will be somewhere in between battery voltage and zero when the battery is between 12.8 and 14.5V.

A thin feeler gauge near the alternator cover should be drawn towards the cover when the field coil is energized.  There must be a magnet to get the alternator make power.  The field coil is part of an electromagnet.

What resistance did the field coil measure?

[Rick Vessell]

Field coil was 4.9 on the meter.  I'll a running check on it also and see if any voltage is present. 

[Rick Vessell]

Problem solved.  The voltage regulator on the combo unit I had installed was bad.  Tested the factory reg and rectifier I took off and both were good.  Reinstalled them and all is well.

Thanks for the help, between you and Hondaman I got it sorted.