Topic: The Ever-Popular CB650 bad charging 'issue', formerly hot start 'issue'

[Frankenkit]

11.2 was at the black and white wires.  These are old brushes, but still well within spec- not worn down to the scribed line yet.

[Spanner 1]

This thread was started November 5th. 2008 and is still going-on unresolved???...methinks there are some forum 'diva's' involved who love the sight of their words displayed for viewing by the forum masses for adulation and 'drooling over'.....just stirring the pot.....

[Frankenkit]

hah. maybe.  I just have this problem, but various things have kept me from really riding and testing- namely a bad gas tank, repeated carb removals/cleanings/reassemblies...

and apparently I'm an asshat when it comes to trying to do this testing, though I've been dedicating several entire days to testing... just somehow none of my results have shown anything useful, probably because I haven't been able to really get out and ride this bike that much, owing to the carbs having never been synched very well 'til now.  (and that nagging probability that if I conk it somewhere it won't start again to get me home)

Trust me, I'm just as ready and excited to blow $200+ on a new rotor, stator or RR as the next person, I just haven't seen anything that definitively told me WHAT I need to be servicing or replacing

Let's go through "known" factors, because Spanner's right. this is kinda ridiculous.
1.  The new headlight is 55w/60w.  Same as stock requirements for the cb650 and an expected amount of draw for the engineering of the system.
2. I've gone through the electrics from the connector for the tail light/blinkers to everything in the headlight bucket and cleaned, polished and dielectric grease sealed everything.  The rate of discharge (or maybe recharge?) has slightly improved after cleaning the ignition switch.  (i.e. the voltage after riding/testing/etc isn't as low anymore. It's gone from 11.6 or 11.8 to 12.3-12.4

3. Still doesn't charge, even when I'm riding at good RPMs.
The bike pukes out 14.8v when I start riding it at 4-5k rpms, but at the end of a ride when it's at operating temp, the same 4-5 grand will only elicit 12.5 or 12.6.

4. Rotor resistance goes from 4.7 to 11.2 at the RR. I have old brushes and I'm not sure how that affects this, as they're still within spec for wear.

5. The RR has reliably tested out ok through this whole ordeal, except with the possibility maybe an aftermarket one would allow me to start charging at lower RPMs like Pinhead says his does.

6. The stator is supposed to be fairly durable.  There is continuity between each of the metal 'rectangles' of the inside of the stator.  Unsure of how to test this during failure conditions.

I think that's everything?
Oh, yeah, and for as many views and posts as this has, there really aren't that many people actually reading the results and posting suggestions.  The 650 system is NOT that different from other bikes, that these test should yield results far beyond the scope of experience of only than 3 or 4 regular posters.

[Pinhead]

With the rotor/field coil being the "weak link" in the 650's, that'd be my first suspect. They've been known to "open" when hot and then start working again when they cool off. Also, I've never gotten the same resistance reading at the coil itself as at the wiring harness (going through the brushes). With the engine running, checking resistance is impossible; the reading will fly all over the place.

With my understanding, if the stator had an open in one of the windings (three-phase, three windings), the system would still just barely charge. I would suspect even an open/bad rotor winding would be able to charge the battery and run the coils if it doesn't also have to run the head light. I would do my next ride and test with the headlight fuse removed.

I haven't read through the entire thread for a while, so I have to ask if you've replaced the regulator? That would be one thing that could easily quit working with heat.

Here is step-by-step of what I would do. First thing's first, you'll need two wires with alligator clips on each end. They'll need to be long enough to reach from the battery terminals to the field coil connecting block under the seat. Note that all of these tests will be with the engine running, fully warm and in failure mode.

You'll first need to get the bike to operating temp and in failure mode. Once the low voltage situation is verified, disconnect the alternator's connector under the seat, and connect the alligator clips to the pair of spade connectors inside the connector. The goal here is to give the field coil full battery voltage.

If your field coil is shorted out as mine was, the light will dim and the engine will probably bog down. If this is the case, disconnect the wires quickly; your rotor is shorted and can start melting wires rather quickly. If nothing obviously bad happens, continue to the next step.

The first option is to pull the rotor spade terminals out of the connector (they'll just "pop" back in when done) and plug the connector itself back in. This way you can keep battery voltage across the rotor via the alligator clips, and the stator's three-phase output stays hooked up to the rectifier and therefore the battery. This will only bypasss one component (the regulator). At this point, check your battery voltage vs RPM's; voltage should go up with engine speed. Note that with no regulator, the voltage should simply keep rising as RPM's go higher. I've seen up to 18v across the battery during a short burst of high RPM, so be careful as you don't want to melt your coils, burn out bulbs, or boil your battery (don't hold high RPM's/voltage for too long). If the system passes this test, than your rotor/stator are good but your regulator is bad and needs to be replaced.


If the previous test failed, the next step is to check the AC voltage coming out of the stator as-is (with the connector completely unplugged, engine running, and battery voltage across the two rotor wires). Be cautious here, as with full battery voltage on the rotor and no load on the stator, voltages can get decently high (I've read of 100+ volts). If the voltage goes up with RPM and all three voltages are pretty close to the same, your rotor and stator are both working correctly. If not, you've got a problem in one of the two components or the wiring to them. **NOTE: The three wires will be outputting AC voltage (NOT DC) and your multimeter must be set on the 200v AC scale.**

If after doing both of these tests, there IS voltage across each of the three stator terminals, your rectifier is fried. Since it's a one-piece R/R unit, I suggest using the Ford regulator and three-phase bridge rectifier combo that I've written about.

If all of these tests fail, I'll have to devise an easy way to test the rotor/stator and wiring when in "failure mode."

[Spanner 1]

O.K., well I didn't read all the way back to Nov. 5th., but did you take-out the starter and clean the commutator  and lube the bushings at each end ? I know this may be old hat ?...done this...

[Spanner 1]

Withdraw all starter suggestions... I just read page 1!

[TwoTired]

4. Rotor resistance goes from 4.7 to 11.2 at the RR. I have old brushes and I'm not sure how that affects this, as they're still within spec for wear.

Oh, yeah, and for as many views and posts as this has, there really aren't that many people actually reading the results and posting suggestions.  The 650 system is NOT that different from other bikes, that these test should yield results far beyond the scope of experience of only than 3 or 4 regular posters.

From my viewpoint, you really can't complain.  I have been asking for pretty much the same data from the beginning. I know how these things are supposed to work, and with the right data reports I can figure out what the issue is pretty easily.  If you chose not to relay the needed data, there is really not much I can do to help.  All I can be is patient.

Anyway...
Assuming that your rotor resistance reading of 11.2 was with the engine stopped (you didn't specify), this is almost certainly a step toward the root of your problem.  There is no valid reason that the resistance should change that dramatically with heat.
The increased resistance makes the magnetic field in the alternator weak, even if the R/R is sending full battery voltage to the rotor.  And, if you had done the voltage with RPM test when hot, I expect you would have determined that the alternator was not doing much to charge the battery.  Whatever power it was making was getting used by the bike, instead of charging the battery.

The next step to take, is it to find out if the rotor itself is increasing resistance when hot, or if there is something in the path between rotor and R/R that adds to the resistance presented to the R/R.

The good thing, is that this type of rotor circuit failure is not likely to destroy a good R/R.

If you do the tests pinhead has suggested, do not EVER connect the battery to the R/R field coil terminals, unless you are dead set on replacing the R/R.  Running the field coil/rotor directly from the battery, won't improve the charging capability of the alternator if the rotor circuit is maintaining 11.2 ohms.  This measurement is pointing directly to the problem.  You now have to isolate whether it is the rotor itself, ot the connection between slip rings and R/R connection.

Cheers,

[Pinhead]

If you do the tests pinhead has suggested, do not EVER connect the battery to the R/R field coil terminals, unless you are dead set on replacing the R/R.  Running the field coil/rotor directly from the battery, won't improve the charging capability of the alternator if the rotor circuit is maintaining 11.2 ohms.  This measurement is pointing directly to the problem.  You now have to isolate whether it is the rotor itself, ot the connection between slip rings and R/R connection.

Just to clarify, I didn't suggest to hook the battery voltage to the R/R itself. Battery voltage should go to the field coil ONLY with the R/R disconnected.

One thing that I forgot to mention, when I was doing the majority of the testing on my bike it was somewhat difficult to get accurate measurements on the field coil. The surface of the copper slip rings had a "glaze" that was inhibiting contact. I had to take a green "scratch pad" and ever-so-slightly scratch the glaze off the surface in order to get an accurate reading.

[Hush]

Yeah Kit, stop holding out on the info 
I'm afriad I get totally lost in the charging circuit having only completed some very basic electronics courses over the years, mostly with me it's "suck and see" or as my tutors used to say "pass the smoke test"
I was interested to read another post by Boxnife and TT advised him to buy a cheap multitester, ha ha it's exactly the same as mine, I wish my old analogue multi hadn't been stolen, I understood that one--it didn't wave around finding all sorts of different voltages and then blanking out when I do try to read it grrr.
So at the end of the day Kit, do you have a "charging problem" or a "hard starting problem"?
I mean if you push the button after a ride and the bike dies, what happens when you arc the solenoid terminals with a big fat screwdriver?
And have you swapped the other solenoid out of the new project bike to see if that has any effect on your starting issues?
Come on it's Sunday...you got no excuse not to try some of our suggestions and report back you posting deva you.

[leekellerking]

B                   M

red/yellow---red/green

red/white---red

---------------
    fuse
----------------


Sorry I can't send a picture, but my camera decided to break last night (right before my 11 year old son blew out the candles on his birthday cake).   


And to top it all off:

  1.  The "new" petcock I got off E-bay leaks worse than my old petcock (which I reinstalled), and
  2.  I now find that the Kreem (or clone) tank lining put in by the owner before last is starting to come loose, so I have to reline my tank.

 

That is the solenoid I have in my 82 Nighthawk 650.  The guy shipped it quickly, too, which was important to me as Bikey was completely down after I broke the old solenoid from uninstalling/installing it too many times. 

I had to rearrange the pinout of the connector, but If I could figure it out without blowing up something, I'm sure that YOU can do it, too.  I can check it this weekend and send you a photo or schematic, if you'd like.

I have had absolutely no problems with the switch since I installed it, although I sometimes fantasize about rerouting the wires a bit to make the install a little more elegant.  (Yea, right). 


Lee

A schematic and pics might help.  ...am i reading this right, in that you had to take it apart and rearrange the insides?  just flipping it wasn't going to work for you?

TT- The reason I had such a long 'wait' for incoming info was that the carbs had sprung a bad leak, so I was waiting for parts, putting carbs back on, fiddling with the carbs and synching because the bike wasn't running right, eventually bringing the bike back home, and here we are now.  Hard to test starting under op. temp conditions when the bike is a) not running b) not in my possession.  Thanks for joining me on the crawl, however it may be.

[Frankenkit]

Ok, to elaborate, the bike was off, because I shut it down in failure mode to make sure it actually was there (just run to the point of not starting again)
and with the bike off, key out, it read 11.2 ohms resistance at the RR's connection to the alternator (the black and white, male spades that plug in to the RR.)

It's raining like hell today so I'll have to wait 'til it lightens up a little to go for a ride to get it in failure mode again. 

TwoTired:
So according to these results, I should get to failure mode, then test the resistance between the sliprings themselves (thereby bypassing the possibly increased resistance within the wires)  and then also test resistance between the brushes and their corresponding black and white spades?

This should then determine where the fault seems to lie, the wiring/brushes or the rotor itself (though brushes are way cheaper), am I right?

Should I also test resistance between the stator wires when hot to make sure they haven't ground/shorted/etc when hot?

Pinhead:
Let me try to paraphrase the directions I've been given to make sure I'm understanding:
While the bike's in failure mode and still running: (to test rotor)
'gator clip wires from battery terminals to the disconnected spades coming from the alternator
(I take it the black and white ones, as you said 'the pair')
If it dims, bogs, starts sucking in most generally accepted ways, the rotor is shorted, there's the problem, disconnect, find a new rotor.)

If nothing apparent happens, step 2: (testing both regulator and rotor's charging ability)
Pop the black and white spades out of the white block connector and reconnect the block connector (the 3 yellows)
Test batt. voltage vs RPMs but not to the point of cooking the battery/blowing lights/wreaking havoc.

3: (if 2 inconclusive)
disconnect the block connector and, while black and white are still hooked to the battery, test AC voltage from all three stator wires (yellows).  Should be decently high. (100vac?) What is a probable minimum I should look for as well?)  If I have decent voltage, rectifier is at fault.

Lee:
Thanks

Hush:
Smartass!

[Pinhead]

Yep, sounds like you know exactly what to do. As for a minimum voltage, that's a good question... I'd say if it gets that far, just report the voltage and if it sounds borderline, Twotired will probably have to chime in.

[TwoTired]

TwoTired:
So according to these results, I should get to failure mode, then test the resistance between the sliprings themselves (thereby bypassing the possibly increased resistance within the wires)  and then also test resistance between the brushes and their corresponding black and white spades?

This should then determine where the fault seems to lie, the wiring/brushes or the rotor itself (though brushes are way cheaper), am I right?

Should I also test resistance between the stator wires when hot to make sure they haven't ground/shorted/etc when hot?

The change from 4.4 to 11.2 ohms is enough of a red flag that I would chase it down with the zeal of a charging Bull.  The fault also fits the theory of poor charging when hot leading to a weak battery unable to deliver the amps need to make the starting motor happy.

I theory, there is nothing in that part of the circuit which would cause such a large resistance variation with heat.    It is a divide and conquer march now, to test and isolate ever smaller sections of the now identified faulty circuit, in order to isolate the single faulty component that is root cause.

The most obvious next measurement, is the the rotor resistance measured at the slip rings proper, instead of a remote reading though a connection medium (brushes, connectors, wires).  If the rotor itself has changed from 4.4 to 11.2 with heat, the rotor is faulty.  Aside from a close examination to see if there is some accessible solder work that has come loose, there would be little else to do beside replace the rotor.  If it maintains 4.4 ohms even when hot, then the variance must be attributed to components between the rotor slip rings and the R/R.
Check the springs that hold the brushes to rotor. Do these become weaker with heat?  Is every pathway connection and wire between the actual brush contact with the rotor and the R/R connection clean tight and properly insulated from any other nearby components?
If the rotor is found to be OK and stable with heat, there is no valid reason why the connective path should increase by 6.8 ohms with the operating engine temperature.

When you find the cause of the 6.8 ohm increase and repair it, then I would move on to other possible causes (like stator issues/ connections), if the "starting problem" persists.

Happy hunting!

[MickeyX]

So my question is... if we find the rotor to be at fault, do we simply have it rebuilt? I think that would be better and easier than trying to get an NOS one. I'm actually thinking it's the rotor but I'm not ruling out a 2nd culprit since the electrics are so old. Along those lines and for peace of mind, I'm thinking replace the R/R as well with a newer, better technology than the original setup. I would like to find one that starts charging at a much lower RPM. I know in it's present state, it's probably "ok" but while we have it apart and testing, just do it. I'm all about preventative maintenance and thinking ahead.
I can chase down and repair/replace any wiring harness issues. It just takes time and figuring out where they all lead to under all of that shrink. I'll get a wiring diagram out and try to get to it tomorrow. I have the knowledge, just not much free time to speak of. Kit has some time but not the background knowledge.
I think she's doing pretty well on her own here. We all sometimes forget that she's never worked on/rode/owned a cycle before. She didn't grow up learning how to do stuff like this. I think she deserves a little slack here, gentlemen. She's also very limited on funds and has to do this around a work and college schedule. Until recently, she had to work out in the elements or at the mercy of the garage owner's hours along with his screwing things up and treating her like sh!t. The sheer fact that she hasn't given up yet is amazing to me. It makes me want to help her even more. If you can't put forth productive and positive information, then simply walk away and don't post here. To come here with one post, make a dig at people and act like an azz is not cool, especially when it is obvious you never read any of this or the build thread.

Thank you to the guys who have been trying to help. Now that the bike is tuned and is otherwise sound, we will retest everything, including what you have added here over the last few days and let you know what we find. 

[Spanner 1]

When my rotor quit on my '81 dohc 750 it was reading about 2 point something ohms...it took me ages to find out what impedance it should have been as Honda don't specify......
Anyway it should have been 4.8 ohms ( from memory ) so lower reading showed a short in the coil....now I was told by the re-winder, who has done 100s of rotors that it's well known that the quality of copper wire used in Honda early 80's rotors was sub-par and almost all fail over time......your bike would fit the description and year!

[TwoTired]

If you can't put forth productive and positive information, then simply walk away and don't post here.

If you are asking me to stop posting then say it. 
I certainly don't want to force upon you what you deem "unworthy".

[mlinder]

If you can't put forth productive and positive information, then simply walk away and don't post here.

If you are asking me to stop posting then say it. 
I certainly don't want to force upon you what you deem "unworthy".

I don't think she was speaking about you, Lloyd.

[mystic_1]

Just as an aside, according to this eBay ad, your bike takes the same alternator rotor as the following:

# Street Motorcycle: HONDA CB650Z / C / NIGHTHAWK SOHC, 79-82
# Street Motorcycle: HONDA CB750F/F2/KZ DOHC Supersport, 79-83
# Street Motorcycle: HONDA CB750SC Nighthawk, 82-83
# Street Motorcycle: HONDA CB900C Custom, 80-82
# Street Motorcycle: HONDA CB900F/F2 Supersport / Bol d'Or, 80-82
# Street Motorcycle: HONDA CB1000C Custom, 83

I suppose (ie wild ass guess) that the other parts such as slip rings etc would be the same also.

Random info.  hth.

mystic_1

[jaknight]

Dear Mickey & Kit,

I have been reading this thread....... I have made no posts because my knowledge is severely lacking in electrics.  TT has helped me before and saved my socks..... I'm still trying to learn electrics. 

I follow this thread, as I do for this entire forum, to learn and gather information and knowledge.  I admire what you (M & K) have done.  Far better than what I could do.  I would like to make posts to help, but I just don't have what you need.  So, I am here learning...... just as you are.  What follows below is for you..... I wish you well.

******
People who do what you do, to the degree that you do, deserve a great deal of accolades for your work. It is very tough for people to complete such tasks but even a greater talent to have a vision of the finished product and make the hands do what the mind's eye sees. The only way to complete this kind of undertaking is exactly the way you are.
******

~ ~ ~ jaknight ~ ~ ~

[MickeyX]

TT - nah man, we're cool. You were one of the guys I was thanking.

It's down right nasty out today, raining sideways and such so we decided to spend sometime at the salvage place looking for parts for the other bike. Kit doesn't have the experience to be out on the wet roads yet and my bent up leg is thumping. Tomorrow is supposed to be decent and in the 50's! Woohoo! Weathermen only need to be right about 30% of the time to keep their jobs, so we'll see.  As Kit has explained it to me, I will test the rotor resistance when cold and then again after I've ridden it for a while at higher RPMs and retest it while everything is still hot. (testing directly on the rotor rings, not the wiring. Got it.) I will also go over the rest of the system from the diagram I posted, (like we did before, but now with an otherwise smooth running bike. thanks again, mlinder  ) while it is cold and then after the ride. TT - I know you gave Kit instrux in her other thread but I will use the diagram since it seems to make the most sense to me with the flow chart setup. (that's just the way my brain works) That way, I hopefully won't miss something or test it wrong. I'll get out my alligator clips so I can do it alone. (Kit works tomorrow)

mlinder - depending on what I find, I won't be riding it over to you guys tomorrow. I don't fancy having to push start it in the middle of Portland if I accidently choke it off at a stop. (I still get lost everywhere to boot, although I'm getting better.) If it's okay though, I'd still like to drop by and run a few things by you guys about the other cb650 and check out the other projects going on. Just for my own knowledge. Maybe I'll come over on the piglet. I NEED a ride, yaknowhutimean? 

[mlinder]

Ah, I was gonna call you and cancel tomoorow anyway, X. A friend of Marcus' girlfirned died on a motorcycle last night, and his garage may not be the place to hang out and work on bikes tomorrow.

[MickeyX]

So sorry to hear that about the friend. Send our condolences, please. If there is anything we can do, just speak up. Will catch y'all later sometime.

[Spanner 1]

Oh I guess its me Ms.X is mad at just 'cos I pointed-out that this thread is going since early Nov !!  I know nothing of the posters circumstances ' has to work outside' etc., just surprised it's not yet resolved, that's all...

[Hush]

Did you put a "spanner in the works" yuck yuck
Ah time is irrelivent when working on these old machines, I expect to be tweeking my 650 till they nail the lid shut.
It's a bit like a crossword puzzle you didn't quite finish and the last word you can't figure is driving you nuts.
I'm just hoping the girls finger this problem for certain so we can all know the solution.

[Frankenkit]

Yeah, while I'm not anticipating plunking down hard-earned greenbacks 'til I have a definitive answer, I AM looking at a RR that promises full charging at 1200 rpms (just a nudge above idle!) a better-wound rotor, and probably new alternator brushes to ensure a cleaner circuit/stronger springs/better connection.

This may be one of those problems with multiple things going wrong, culminating in one more tangible failure,  but working as I have time and can afford it, there's no reason why new technology can't update these old bikes while keeping the look and feel pretty stock.