"UPDATE" 2 :: Battery not charging ::

[2nafist]

Still waiting on my service manual in the mail.  Downloaded a version online, but the electrical diagrams in the charging system aren't giving me a good enough idea of what is what.  Might be numb-skulled, but is this green wire supposed to be grounded to something?  What is this little module?  Trying to track down why my battery wont charge when the bike is running.  I have also read mixed things concerning this.  1979 CB750, should the bike continue to run once the battery is unplugged or not?  Mine does not, and I will do my best to trace and test backwards from the AC generator to find out why the battery isnt charging.  In the meantime, can you tell me what this thing is and if this wire should be connected somewhere (ie grounded)?
Thanks

[Half-Caf]

Looks like thats your blinker module.
Also, if thats the green cable I think it is, it should clip onto a tab on the right side of your battery box.
Ad yes, dark green is ground on these bikes.

[icerigger]

First things first, the infamous green wire doesn't go anywhere, it's just there.

As far as charging, they don't start charging until high revs, over 3K so if you pop the battery out, it will stop.

A voltmeter across the battery should read 14-15 V at 5K rpm, if not it'll never charge. Most likely the rotor is shorted, should be > 4 ohms across the rings. Next most likely is the regulator and then the stator. The FSM has good info on testing the whole thing.

And yup, that is the signal blinker.

[2nafist]

good info, thanks a bunch, ill check back

[seestheday]

These might help

http://home.earthlink.net/~trinomial/DOHCcharge.html

http://www.cb750c.com/publicdocs/EFT/Elect_Trblshtng.pdf

[2nafist]

So far this forum is THE TITS, ha.  Got this bike less than a week ago, and already finding some very much needed help.  Thanks, I'm sure I'll be here a while.

[2nafist]

UPDATE::
Thanks for the help, as for the update, its kind of a long story.  
Bike is still dying.  In fact, it died as I pulled up to the T to take my license test today.  So, that was awesome.

Bike has ran for the past week or longer, haven't needed a charge.  Also have only been riding it around the block.

All that can wait.  Tested the stator using the manual and ohmmeter. Resistances on all 3 yellows are equal.  Took the R/R off and tested in accordance to the manual.  Pics below.  Please correct me if I have used the meter incorrectly or anything

One lead to green ground, one to each of the yellows.  All readings are around 700, with the meter in the 2000k position

Switched leads below...couldn't get a reading in any position...okay, not sure if that's what the manual means by one way very high resistance, and one way very low resistance...

Moved a lead to the Red/White connection as per the manual.  Same thing.  Around 700 one way, no reading? the other...


Again, when the bike is running, even up to 5k RPM, the voltage reading on the battery is at a total loss.  Meaning below 12v, especially at 5k rpm.  Any ideas???

[icerigger]

Check the rotor. These things use an active rotor and often the coils short out. Pull the cover containing the stator off the right side and check the resistance across the two slip rings. Should be > 4 ohms. Any less and the rotor won't produce a high enough magnetic field to excite the stator.

[sgtslag]

Reversing the leads on the meter, reverses the polarity on the Rect./Reg.:  it will only pass current one way, which results in a reading with one polarity, and nothing in the opposite.  Essentially, this test checks the internal diodes of the R/R unit.

You did not mention this, but with regards to running a bike and disconnecting the battery...  Don't!  The battery acts as a load for the Alternator, and without said load, the Alternator, and all of the electricals on the bike, can be destroyed, by a massive surge in current.  This is true for all bikes/engines equipped with a generator/alternator; a magneto system is different.

The DOHC bikes have an electro-magnet system, within the alternator, which produces much more current output than what an alternator equipped with much weaker permanent magnets can ever produce.  It relies on current from the battery to energize the alternator's magnets (electro-magnets), in order for it to generate electricity; without the current to activate the magnets, there is no magnetism, and no electricity generated.

I recommended this book, yesterday, in another thread.  It explains the basics of electrical systems, and troubleshooting, on motorcycles.  It does a very good job of explaining things.  It is worth the money, and the time, to study it.  I am an "expert" in electronics/computers, and even I learned some useful things from it:  Amazon Link.

Based on your description, it sounds as though your charging system is not working:  the bike will run, for a while, off of the battery's stored charge; once that is gone, it won't run at all.  If you discharge the battery to the point where it won't run the engine anymore, it is called "deep discharging" -- this will kill a flooded battery, very quickly, requiring a replacement, no matter how new the battery was...

Follow the manual for troubleshooting the charging system (checking the alternator's rotor, as mentioned already).  If you don't get the specified results, the manual should tell you what to fix/replace.  Once that is done, you can put a known good battery in the bike, and connect your Voltmeter across the battery's leads, then rev the engine up to 3,000 RPM:  it should show ~14 Volts across the battery, if the entire charging/regulating system is working properly.

Here's a simplified breakdown of the electrical system:

A)  Alternator generates AC voltage/current (three phase, three yellow wires).

B)  Rectifier converts said AC into DC (Black/Green wire:  negative, or ground, same thing in this circuit; Red wire:  positive; most of the electrical components on the bike require DC, not AC).

C)  Regulator (contained within the Rectifier unit) keeps the Voltage from climbing too high, which would burn out the lights, the solid-state ignition system on DOHC engines, and the Battery (would boil off the electrolyte, destroying the lead plates within -- new battery needed, very quickly).

D)  The DC current/voltage runs the lights, the horn, the alternator's electro-magnets, the ignition system, the sensor (oil pressure), and it charges the battery without destroying it.

Cheers!

[2nafist]

Thank you for the good info and the replies, much appreciated.  I forgot to mention that I had already checked the alternator / rotor per the Clymer instructions.  I did this prior to checking the R/R, and everything seemed to check out okay.  The battery is suspect, and I will get a known-good battery to put in an test the voltage again.  Question:: With a full charge on this suspect battery I have now, and the bike running at 5k rpm, should the voltage across the terminals read 14v~?  I believe the last time I did this, it was at a loss (11.3~).  I am going to check all connections, grounds etc.  The R/R looks to have been replaced prior to my purchasing of the bike (the wire wrap being bright blue, and it looks out of place for everything else on the bike).

[sgtslag]

With 11.3 Volts, at 5k RPM, your charging system is not functioning, and you are running off of the battery -- it likely won't start the bike at that voltage level.  Yes, it should read ~14 Volts at anything above 3k RPM.

Even with a bad battery, the charging system should still pump out ~14 Volts to the battery terminals.  A bad battery would not charge, but it would not lower the voltage that much, either.  Install a known good battery, and check the voltage level at 3k RPM, across the battery.  If the charging system is not working, it will read less than 12.7 Volts.

An AGM battery is the best, if you can afford it:  won't discharge during winter storage, no need to remove it; sealed, no maintenance required; can last 2+ times as long as a flooded cell (standard) battery; usually has more CCA for starting; less damaged by deep cycling, but don't try it...

Also, a volt-meter installed on the bike, is a very good idea.  Here is a very affordable unit type (can be purchased anywhere, this is just an example):  Amazon voltage monitor.  A fuse-protected, accessory outlet/cigarette lighter plug is a very nice accessory on any bike, useful for charging your cell phone, or powering a GPS, when riding.  It will also serve to power this charging system monitor (glance at it, occasionally, when riding, to make certain the charging system is working properly, and you most likely won't get stranded again).  Cheers!

[2nafist]

I meantioned in the pictures that the R/R was reading 700 in the 2000k position.  Is this high enough?  I'm not sure what this means, if 2000k is a high or low number reading

[2nafist]

Bump plz :(

[Hoosier Daddy]

the 200K setting moves the decimal point on the scale of your meter. Allowing you to read higher resistance more accurately than the 200 scale.
Lets say you were measuring a circut that had 3000 ohms... at the 200 ohm setting it would read open or infinite, because it is more than 200, where on the 200K setting you could read the proper 300, but it may have displayed a decimal point in it ".300" and you do the math in your head.

[2nafist]

The manual doesn't really state a specified resistance.  All of the resistances match, which would seem correct, but is it enough?  Is there any amount that is too much/too little?  700 is what I'm reading at 2000k.  This is what I meant to post in my prior replies.

[Hoosier Daddy]

I posted a link to the CB1000C manual in the Documents section here a while back, It gives more detail on the charging system troubleshooting. Damn good help there.
CB1000C_Manual/Chapter Battery - Charging System.pdf

If you go to page 18-9 it says resistance should be between 5 and 40 ohms with your meter on lowest setting.

[sgtslag]

Check to see if your meter has a Diode Test Mode on it.  If it does, use this, and the schematic shown in the previous post.  The Diode is a one-way gate for electricity:  it only allows electrons to flow in one direction, blocking flow in the opposite direction -- when Alternating Current (AC) is applied to it, it blocks flow until the AC is of the correct polarity, then it conducts most of it (rectifying/turning AC into DC, or Direct Current), dropping 0.6 Volts across itself, if it is a silicon Diode [germanium Diodes are only used in very special situations (more expensive to make, less durable than silicon), and they drop only 0.4 Volts?].

Anyway, by using the Ohm-meter, you cannot guarantee a proper resistance reading, unless you know that your Ohm-meter will apply a particular voltage, on a particular resistance range...  The Diode Test mode applies enough voltage to turn the Diode on, and it measures the voltage drop across it, checking to see that it is 0.6 Volts, verifying that the Diode is working properly.  This is the only way to be certain that your R/R is working properly, unless you have the same Ohm-meter as what Honda engineers were using when they wrote that manual.

Remember:  using the Diode Test Mode, you will only get a passing reading (usually a beep, accompanied by a numerical reading, varies by meter -- consult the owner's manual) when the polarity is correct; the reverse polarity should read as an open.  This applies to the Yellow/Green wire tests (individual Diodes shown in the schematic diagram).  Cheers!

[2nafist]

::  Issues persist  ::

Rode for two days to and from work.  Upon arrival home last night bike won't restart.
Been carrying my voltmeter around with me, and battery voltage was slowly dropping over that time from 12.7v~ to 11.2?v~.  Generator slip rings resistance is >4ohms.  Referring to past posts, numbers on R/R are the equal in both directions (700~ one way, 0 the other) which indicates ok? R/R?  Stator numbers are equal as well.  Battery charged up and is running for those two days with normal riding.  Still looking for a good battery before buying one just to make sure.  But as stated before, the voltage should go up if the bike is running, and the charging system functions...

ANYWAYS

When the bike is running day one  :: at 5k RPM, the voltage across the terminals does go up, never above 13v though

Day two  :: at RPM, overall voltage drops, both at idle, and at 5k.  Now well below 12v.
I have never seen the voltage go up to 14v.

Bad connection?  Ground?  My graphite? Spring loaded posts in the stator are not near the wear marks, still about 1-2cm left til the marks.  
So, can you tell me where exactly the ground wire in the harness goes when it leaves the R/R?  I get lost following it up to the headlight.  Does it just end up using the main battery ground?  Any other thoughts on this?  Thanks for all the help so far.

[sgtslag]

Not sure what the issue is, but the negative terminal of the battery is "ground", and it is connected to the chassis of the frame of the bike, hence the term, "negative ground system", as the negative battery terminal is connected to the vehicle's body/chassis/frame; if the positive battery terminal were connected to the body/chassis/frame, it would be a "positive ground system"...

To check the grounding of the system, connect either DVM terminal to the negative battery terminal, and touch the other terminal to various points on the bike to verify a good ground connection:  the R/R outer metal case (<5 Ohms, if connection is good); body frame of bike (unpainted metallic point); negative side of lights on bike; etc.  Cheers!

[2nafist]

Sorry Slag, i think i sent an email to you on accident just now.
Okay
Testing from (-) batt terminal to R/R makes the meter to crazy.  To unpainted areas of bike is stable <5 ohms.  And I'm not sure what you meant by "negative side of lights on bike".  Does this indicate a bad connection of RR to bike?  Also, I think I found the diode setting on my meter, I'll read thru the previous posts in this thread for whoever told me about that test and try it out.
Thanks Slag

sgtslag wrote

Not sure what the issue is, but the negative terminal of the battery is
"ground", and it is connected to the chassis of the frame of the bike, hence
the term, "negative ground system", as the negative battery terminal is
connected to the vehicle's body/chassis/frame; if the positive battery
terminal were connected to the body/chassis/frame, it would be a "positive
ground system"...

To check the grounding of the system, connect either DVM terminal to the
negative battery terminal, and touch the other terminal to various points on
the bike to verify a good ground connection:  the R/R outer metal case (<5
Ohms, if connection is good); body frame of bike (unpainted metallic point);
negative side of lights on bike; etc.  Cheers!

Quoted from:
http://honda-cb750-s.456789.n3.nabble.com/UPDATE-2-Battery-not-charging-tp4039420p4041482.html