Topic: 1976 CB750K Charging issue

[Rsnip988]

1976 CB750K Charging issue

For the record it didnt charge when i bought it... and i have searched the forum for answers before posting

What I have done:
1.  Rewired bike from front to back with new connectors, rechecked for shorts found none
2.  Replaced regulator with a good new one
3.  Replaced rectifier (even though the origional passed the clymer testing procedure)
4.  Pulled off the covers and cleaned the connections to the alt parts that were in the shifter housing
5.  A. Pulled off the cover containing the Sator & Field coils
     B. tested yellow leads no resistance between so it is fine
     C. to test the white and green wires the manual is somewhat vague (or i dont know what it meant) about testing one of the wires against the "core"
6.  It is a new battery also I have been "tending" with a trickle charger after draining by riding

I know the stator tests ok,
Can the rotor go bad since its just a piece of metal on the rod?

Is there a way to test the field coil other than the shop manual way, an easier to understand way i mean?

if theres anything i may have missed testing let me know
thanks in advance

[TwoTired]

Take your ohm meter, set on lowest scale, and place the probe tips together. Note the display.  Subtract this reading form future measurements.

Disconnect the white and green wires from the regulator.  Measure ohms across the White and Green.  S/B 7-ish ohms.

The stator yellow wires should have about .2 ohms between each other, and infinite between any of them and the engine case.

Unlikely, it is a rotor problem.

If you are good so far. Then measure the voltage of the black wire to the regulator.  Move the black reference probe from the nearby green wire connection, to the battery negative terminal.  The two readings  s/b the same with the keyswitch on, or your wiring is suspect.

(You did use the stock wire color convention, right?  Or, are all your new wires black 'cause that looks cool?)

With the key switch on and the battery below 12.6 V, the white wire going to the alternator should have full battery voltage at the regulator connection.

Enough for now, your turn to report findings.

Cheers,

[Rsnip988]

(You did use the stock wire color convention, right? Or, are all your new wires black 'cause that looks cool?)

no but i did use color coded wire & elec tape for labeling, and i wrote them down for future use

I shall report the results as soon as my multimeter finsds its way back to me

(its in my wifes trunk and she'll be back tonight)


I knew i could count on you TT for some sort of elec help

thanks

RKS

[Rsnip988]

The white and green did indeed have 7.3 ohms between the two

the yellow wires also had the proper 0.2 ohm between all of them

the odd thing with the wiring is that everything works the way its supposed to except the charging system,

I did notice one or 2 wires that the PO had placed in strange places, the green wire going to the reg had been spliced into and one end went to a ground

Another oddity i found was that the R/G wire coming off of the solenoid (which i thought was supposed to be black) was running to the ground in order for the starter button to work, i tried taking it off and using the positive termional but that didnt work either, it needs to be grounded to start but then if you take it off nothing happens (because its the starter solenoid i guess)

I'm going to go over the K3-K7 diagram and compare it to the "Simplified honda diagram" here
http://www.sohc4.us/forums/index.php?topic=17262.0

i noticed that there are serveral wires that are supposed to go to the Starter motor safety unit that were just clipped off where they came from, how is this bypassed safely, or is there a way to cheaply replace it

is there a test to check the regulator unit, the manual said to check the "testing section" but i was having troublke finding it, probably because i was royally ticked off at the bike not working

 
Thanks again
RKS

[TwoTired]

is there a test to check the regulator unit, the manual said to check the "testing section" but i was having troublke finding it, probably because i was royally ticked off at the bike not working

Uh, yes.

If you are good so far. Then measure the voltage of the black wire to the regulator. Move the black reference probe from the nearby green wire connection, to the battery negative terminal. The two readings s/b the same with the keyswitch on, or your wiring is suspect.

That was the first step.  To establish some wire connectivity.  The next step is to measure voltage on the white and green wires with the key switch on.  After we establish that the alternator field is indeed powered by the key switch, then we tackle the electrical path from stator to rectifier, then from rectifier to both battery connections.  After we establish that the alternator is making power and it is being delivered to the battery, THEN we can find out at what voltage the regulator limits power delivery to the battery.

Passing comment:  Electrical devices do not respond in any way to personal rage.  Emotions don't have much in common physics.  Physics is very much dominant in electrical behaviour.  Getting ticked off at an inanimate object seldom benefits either object or human associate.  Most often it is bad for both.  The disspasionate approach seems to be the most productive and benificial for both machine and human interaction.

I recommend that you get your charging system sorted first.  Move the mountain in small pieces.  You HAVE established that your alternator should work when all the connectivity physics have been addressed.  That's one part of the mountain you don't have to move.  Then move on to the starter saftety unit, etc.  Divide and conquer.

One step at a time.

Cheers,

[Rsnip988]

After making sure all of the components worked individually, i started tracing wires like you said after seeing no continuity between the black wire from reg to the positive post, and it seems the PO had accidentally wired it to some ground wires in the front insterad of the ignition

So I wired it back up properly and it seems to charge between 13.2 at idle and 15.2 @ 6k rpm

since my battery didnt die while riding I think I fixed it

Thanks TT

you are right of course about emotions not influencing inanimate objects
but i think all of us know what its like to have been there

[TwoTired]

I'm very glad to hear you tracked down the problem!  Well done!

15.2 is a bit on the high side for charging.  But, when your battery is at full charge and the engine running at 5-6K RPM, if the battery doesn't look like it's boiling, you should be okay.  If it is bubbling inside, then the VReg needs to be tweaked to lower the peak voltage.

You're right about us all being in the rage place from frustration.  But, it is important to know what actually got the job done and how goals were achieved.  A methodical, reasoned approach can help keep the blood pressure lower, which may become important later in life.

Congratulations and of course...Cheers!

[Rsnip988]

I hav an AGM battery (one of the $60-70 ones) so theres no visibility to see if anything can boil, will this be a problem?

I know i can adjust the points in the Reg (and will if i can ever find the feelers i misplaced)

[TwoTired]

I don't have any direct experience with AGM batteries.  What does the manufacturer say the peak charge level is supposed to be?

Cheers,