CB650 charging issue

I need advice from someone knowledgeable re: bike electrics -- if you have
to guess, I appreciate the help but I have a question whose answer may leave
no room for error.

I got a creamer 1979 Honda CB650 with exceptionally low mileage for a steal
because a guy died and left it to his middle-aged non-biking sister. It has
the charging problems typical to those bikes. I have researched the issue
online, gotten hold of the protocols of diagnoses, and read, read, read,
about it.

I was able to do the simplest diagnostic tests such as checking, with a new
fully-charged battery, to see if the voltage increased when revving to the
given 5000 rpm. There is nothing there but the battery voltage, and if I
drive it awhile the voltage drops significantly toward dead and will
eventually kill even the engine. I don't need any more evidence that the
charging system is kaput. Further, I meticulously cleaned every connector,
even though they were all already clean and uncorroded, and it made no
difference. I have no access to a shop, and no desire to do any of the many
more technical tests -- would rather simply install new parts.

I intend to replace the regulator/rectifier (one component) and/or the
rotor. I read from an expert who says the stator is the least likely to go,
and if it does it is usually a case of some things burning up, of which
there is no obvious hint so it seems like that should be the last thing to
consider. I know that, in the case of car electrics, it can matter which
components you replace first inasmuch as if you do it in the wrong order a
bad component can cause the replacement of another part to fail. I am
wondering if any similar conditions pertain to CB650s since I would
naturally like to replace the parts starting with the least expensive.

So, what is best -- replace the rectifier/regulator first and if that
doesn't solve the problem go ahead and replace the rotor too? Or the other
way around?

Thanks in advance,

pflu

 

Wait a couple of days to see if an expert or two here gives some cogent
advice!


I'm not one of them, but from what little I know, would think if you can
check battery voltage, it won't take more than a couple of minutes to
check stator output (eg., you may have to remove the seat). That might
certainly help to isolate things to a useful degree. Could save quite
a few bucks plus lots of wasted time obtaining parts one by one.

 

How about checking the alternator brushes before buying parts you
might not need?

 

Why not find out which component is duff before you start throwing bits
at it in the hope that the right one will stick?

Check if the alternator is actually working first - ie, measure the
output which is normally stated in the workshop manual - and if it's
dead, replace the rotor. If it's not dead, replace the reg/rect.

 

I appreciate the suggestions you all have provided so far and will follow up
on them all. Thing is I am pretty much dependent upon the internet since I
live about 159 miles away from any shop, and I possibly sound naive inasmuch
as I am trying to narrow down what is an overwhelming amount of detail on
the technical forums -- it's not that I wouldn't want to go there but am
limited to a multi-meter out here in the woods. I can't afford to do more
harm than good out of an admitted ignorance of bike electrics, and most
advice assumes you can run down the block to get stuff.

That is not to say, however, that I am ignorant re: motorcycles. I started
out with A Harley 74 back in the day when a chopper meant removing the front
fender leaving a bare wheel, and cutting it down to use as a rear fender.
All the ramp jumping, trail riding through the woods, etc. was done on those
big babies and you wouldn't believe the agility some riders had with
manhandling those monsters doing tricks. Since, I have pretty much covered
the US on various sized Hondas, having fixed chains at 3 a.m. on an
interstate using a penlight with concrete highway marker for an anvil --
that sort of thing. So for any of my friendly pussy-hearted flamers whose
succinctness ends at "**** you", I would be happy to invite you to come up
here to Northern Minnesota rather than hide behind the anonymity of Usenet,
where I would be happy to rip your face(s) off and tuck it under your poopy
diaper; the bigger pile of shit, you are, the better.

If I tax anyone's patience with further questions I apologize, inasmuch as,
like you, I try to do the best I can. Thanks.

pflu

 

, would think if you can

Paul,

Can you elaborate -- how do I check the stator output? Is that the one where
you measure the voltage across the battery with the engine at fast idle?

pflu

 

How about checking the alternator brushes before buying parts you
might not need?



OK, that will be the next thing I will do. Thanks,

pflu

 

If the brushes are OK, you can probably disconnect the field leads
from voltage regulator and excite the rotor field with 12 volts DC
direct from the battery and see if that raises the output voltage
while the engine is running.

The voltage regulating function of that type of regulator is just a
transistor which is
turned ON when the ignition key is ON, and then it turns OFF when
battery voltage rises above 14.5 volts.

We discussed CB650 alternators EXTENSIVELY in this group about two or
three years ago, and, AIR, the field leads are the black and white
wires. One CB650 rider e-mailed me images of the pages from his Clymer
or Chiltons manual, but I deleted them already.

 

Phluge wrote:
....

If I've got it right, that one tests the whole charging system (except
for the battery), not the stator/alternator output by itself. I found a
wiring diagram at

http://cosky1.tripod.com/index.html


under the seat there will be a multi-wire connector that joins the
alternator to the reg/rect and probably three of those wires will be
yellow in colour (plus two more, one black and one white). You can
check the yellow ones in pairs, eg., uncouple the connector then check
each yellow to one of the other yellows, with the meter set to AC
voltage - if the alternator is working fairly well, on each of the three
pairs you should see much more than 12 VAC, perhaps as much as 30 or 40
VAC when you have the engine revving fast, say 4000 or 5000 or more.
That would tell you there is good chance there is nothing wrong with the
alternator.


I see there is another post from "." about testing the reg/rect itself
with battery which would help point the finger at that part if it is bad.


As I said, I'm not an expert, my electrical trouble-shooting skills are
so amateur that nearly always I have to refer to an online source or
an electrical troubleshooting book, but not always the factory service
manual (it seems some of the typical resistance tests in factory manuals
aren't always helpful because while they may tell you a part is bad,
they don't assure you the part is good).


Not telling you what to do, bu a couple of sources I know of, eg. on the
www are:


http://www.motorcycleproject.com/ gives some tips, one I like is how to
make a high current shunt.


Some shortish books that I know of are


"motorcycle electrics without pain" by Mike Arman

"motorcycle electrical systems" by Tracy Martin

 

Oh, here's another link to a nice simple guide that one of the regulars
here mentioned a few weeks ago:

http://www.electrosport.com/technical-resources/library/diagnosis/pdf/fault-finding-diagram.pdf

 

Someone posted quite recently with a similar problem - they cured theirs by
cleaning the slip rings under the brushes.

 

That's usually a stop gap fix. Worn out or sticky brushes don't make
good contact, and a black film begins to coat the slip rings or
commutator segments.

 

No, I was talking about manually exciting the rotor field by applying
battery
voltage across the B and F terminals.

 

Oh sorry, I guess you are talking about testing the rotor and stator in
isolation?

 

If the brushes are OK, you can probably disconnect the field leads
from voltage regulator and excite the rotor field with 12 volts DC
direct from the battery and see if that raises the output voltage
while the engine is running.

The voltage regulating function of that type of regulator is just a
transistor which is
turned ON when the ignition key is ON, and then it turns OFF when
battery voltage rises above 14.5 volts.

We discussed CB650 alternators EXTENSIVELY in this group about two or
three years ago, and, AIR, the field leads are the black and white
wires. One CB650 rider e-mailed me images of the pages from his Clymer
or Chiltons manual, but I deleted them already.


I don't doubt that a bit -- from the looks of the forums I have found it
seems like every owner has had these problems, has input re: solutions, and
leaves a guy-who-can-barely-interpret-an-ohmmeter's head spinning. I have a
few pages printed out from a manual, have followed their diagnostic
instructions as close as I can figure. Here are the results I got: (I used
the 200ohms scale on a digital meter)

1.Brushes are fine -- at least 10mm above the mark. I did not try your
suggestion to excite the rotor from the battery yet, I have the oil drained
and a new filter bolt on order -- plus I'd be scared a little shitless.

2. Stator test: Continuity between all yellows is .9. Book calls for 0.5 -
1ohm. I don't understand these scales, it just says replace if there is no
continuity. Ther was no continuity with anything for the black or white
wires, none with any to ground.

3.Rotor test: It says some very low resistance should be between the slip
rings (approx. 4-6ohms). My meter jumps all over between about 10 to 175 on
the 200ohms setting -- I don't know what that is all about. There is no
continuity between rings and ground. It says that most of the time when
rotors are bad there will be either infinite resistance (burnt out) or less
than 2ohms, (meaning internally shrted.)

4.Voltage Regulator test: "With ignition on, bike not running, you should
get less than battery voltage between the black and white ires from the
regulator." I get 0.00 Volts.

4. Voltage regulator performance test: Voltmeter between + and - battery and
rev engine. Says it is supposed to prevent it from going over 14-15V, but
there is no change at all in volts at 5K rpm.

RE: the regultor/ Rectifier test: The manual makes me crazy here. It tells
you to measure between the green rectifier lead to each of the three yellow
leads in both neg and pos directions (should all be the same , HIGH or LOW
with opposites between polarities). Do they mean to measure WITHIN the
rectifier or BETWEEN the rectifier and alternator leads? Then you measure
between the red/white and the three yellows, one direction, all must be the
same either high or low -- again, within or between the alternator?

Does the fact that this bike has only 8,061 original miles give you any
clues? The brushes seem barely worn.

I'd truly appreciate any interpretation you can offer about my clumsy
attempts at measuring. The mosquitoes are out in full force day and night
and they cetainly love it that I am out there sweating. Thanks,

pflu

 

I did clean them when I measured their resistance etc. -- they were a bit
filmy while the brushes are fine.

pflu

That's usually a stop gap fix. Worn out or sticky brushes don't make
good contact, and a black film begins to coat the slip rings or
commutator segments.

 

Just my three cents of coourse:

1) I believe one measures the rect/reg right on its terminals.
2) I still think it's best to do a dynamic test of the alternator
output, if that shows healthy voltages you could probably eliminate the
alternator as the problem. Lots of factory manuals say to do that even
if this one doesn't.
3) Also, I was assuming the battery is good, but was just wondering if
perhaps there is a blown fuse between the reg/rect and the battery?

 

paul c wrote:
....

Or just a bad connection/chafed/loose wire?

 

paul c wrote:
....

Or just a bad connection/chafed/loose wire?

 

Battery is brand new.

The fusible link is good, all the connections are sound and clean and there
are no damaged wires. I cleaned everything even if it looked good. Other
than a few riding dings this bike is pristine -- was kept indoors and hardly
ever driven (avg. 278 miles/year).

I have seen most of the links you gave, printed out some stuff including the
"Fault-finding" diagram --thing is I am up to my ears in tests and results
that I'm not sure I know how to interpret at this point. Like I said, I have
a digital multitester I barely know how to use (but I'm a persistent
son-of-a-bitch, the kind they would have liked to have on board Apollo 13. I
will worry a problem until it gets solved).

I did all the running type tests last week before draining the oil out and
I'm waiting for delivery of a new filter bolt before I can do any more.

I certainly appreciate your help.

pflu