Topic: 1980 cb650c not charging (I did my reading)

[Modest_Man]

Hey guys,

Just recently bought my first bike, 1980 cb650c.  It had been sitting for two years so I got it running, runs like a champ for 30 minutes then dies.  Came on here and did tons of reading, went out and bought myself a multimeter to test my electrical system.  I'm new to motorcycles and electrical systems, so bear with me if I did something wrong or leave out vital information.

Bought a new battery (old one was toast).  Trickle charged it until it was full, voltage reads 13.5V.  Battery is good.

After letting the bike warm up I turn on the high beam and rev the engine to 5k rpm, voltage reads 11.68V.  Definitely not charging.  Turned everything off and disconnected the battery ground.

Tested the stator, going yellow wire to yellow wire.  Resistance reads 1.1-1.2 ohm between the three of them.  Manual says .41-.51 is the specified resistance.  Going all 5 terminals to ground I get no reading (multimeter manual says when the input is at open circuit the figure "1" will be displayed for the overrange condition).  I think that's what I want, not quite sure on the 5 terminals to ground.

Tested the continuity rotor, got a resistance reading of .5 ohm between the two slip rings.  (Book says .4-.5 ohms is good).  Checked between the slip rings and center core (do I need to remove the bolt securing the rotor to test this?  If so I did not test this correctly.  The center core sticks out slightly so I just prodded it with the multimeter with the bolt in.)  Multimeter showed no reading (the "1"), so overrange which I'm assuming is infinity.  If I did this correctly I think the rotor checked out.

For the voltage regulator/rectifier I got no reading for every test I did.  Green to the three yellows and reversed, as well as red/white to yellow.

So, from my limited knowledge and experience (practically zero) it appears to me that my regulator/rectifier may be toast.  Hopefully I can get some of you resident experts to either confirm or deny this.

And lastly a quick shot of my $300 bike.  Anyone know where I can get a "normal" seat?  This was owned by a small woman before me and I sit way to forward over the tank.  The rack is leaving as well.

[Modest_Man]

Nothing?  I figured this would be pretty easy for someone with more experience than me to say yay or nay to my assumptions.

[L.A. Nomad........]

I bet money it's going to be the rotor, you'll have to buy the removal tool. And you'll need to have it rewound. The ohms test checked out OK too!

My buddy had the same problem! After reading everyone's trouble shooting tips, it almost always end up being the rotor!  My friends rotor had a burnt spot on it..

Remember I'm only being suggestive.....

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[Modest_Man]

Ok, just messed with the voltage regulator/rectifier again.

Ends up I didn't have my multimeter on a high enough ohm setting.  Book says 2,000 ohms minimum, I'm well over that.

With the red multimeter lead in the green lead and the black multimeter lead in the three yellow leads I get readings of 135.2, 115.8, and 141.5 at 200k ohm.  Reverse the multimeter leads (black in green and red in yellow) and I don't get anything at any ohm setting (200 up to 20M).

Black multimeter lead to the red/white lead and red multimeter lead to the three yellow leads gives 135.7, 133.1, and 126.1 at 200k ohm.  With the multimeter leads reversed (red to red/white and black to yellow) gives 13.1, 12.6, and 10.3 at 20M ohm.

Defective or not?

[mlinder]

TT should be by shortly to help you out with this

[TwoTired]

Bought a new battery (old one was toast).  Trickle charged it until it was full, voltage reads 13.5V.  Battery is good.

OK.  Battery probably IS good.  But, that voltage is with the surcharge right off the charger.  Normally, you let it rest without charger for about two hours.  It should read 12.6-12.8V for a good battery.  Just a test procedure comment.

After letting the bike warm up I turn on the high beam and rev the engine to 5k rpm, voltage reads 11.68V.  Definitely not charging. 

agreed. Not good.  Voltage should be higher, or at least showing a rising trend, indicating the battery is receiving/increasing charge.

Tested the stator, going yellow wire to yellow wire.  Resistance reads 1.1-1.2 ohm between the three of them.  Manual says .41-.51 is the specified resistance.  Going all 5 terminals to ground I get no reading (multimeter manual says when the input is at open circuit the figure "1" will be displayed for the overrange condition).  I think that's what I want, not quite sure on the 5 terminals to ground.

For resistance measurements this small you need to place the meter probe tips together and then subtract the reading on the display from future measurements on this scale.  Your test leads have a small resistance on their own.

Tested the continuity rotor, got a resistance reading of .5 ohm between the two slip rings.  (Book says .4-.5 ohms is good).  Checked between the slip rings and center core (do I need to remove the bolt securing the rotor to test this?  If so I did not test this correctly.  The center core sticks out slightly so I just prodded it with the multimeter with the bolt in.)  Multimeter showed no reading (the "1"), so overrange which I'm assuming is infinity.  If I did this correctly I think the rotor checked out.

Your book is wrong.  Or, you misplaced a decimal point.  The rotor should read between 4 and 5 whole ohms.  0.5 ohms shows a nearly shorted rotor needing replacement.

For the voltage regulator/rectifier I got no reading for every test I did.  Green to the three yellows and reversed, as well as red/white to yellow.

The rectifier needs a special scale selection to place enough voltage on the diode to activate it.  Looks something like this   -|>-

So, from my limited knowledge and experience (practically zero) it appears to me that my regulator/rectifier may be toast.  Hopefully I can get some of you resident experts to either confirm or deny this.

The regulator may indeed be bad.  If the rotor has this low a resistance it will draw lots of current through the regulator.  This may or may not damage it with this overload.  You'll need to test its output when presented with the proper r4-5 ohms on it's output.  It should have whatever low battery voltage there is on its output.  If not, THEN it's toast.

[Hush]

Hush's 50 second cure for 650 charging probelms.

Borrow/lend/steal/hire another regulator/rectifier and plug it in to see if this helps..yes OK buy new reg/rec.
NO.........ignore your rotor reading and replace it, they test fine but go bad, not sure how but it usually comes down to the rotor (not the stator, some confusion here, stator is wound wiring thingy that runs around rotor like a halo)

Rotor...rotor...rotor.....damn 650 poxy dead rotors.....one of the 650 guys on here is into his 3rd rotor replacement, same model as yours too.
I did all your tests and found zip, I swapped the rotor and haven't had to do anything more to the bike, leave it for 2 weeks and she fires straight up...honestly.
Even the book doesn't help with our bikes, it's like they are haunted in the charging dept.

[Modest_Man]

Bought a new battery (old one was toast).  Trickle charged it until it was full, voltage reads 13.5V.  Battery is good.

OK.  Battery probably IS good.  But, that voltage is with the surcharge right off the charger.  Normally, you let it rest without charger for about two hours.  It should read 12.6-12.8V for a good battery.  Just a test procedure comment.

After letting the bike warm up I turn on the high beam and rev the engine to 5k rpm, voltage reads 11.68V.  Definitely not charging. 

agreed. Not good.  Voltage should be higher, or at least showing a rising trend, indicating the battery is receiving/increasing charge.

Tested the stator, going yellow wire to yellow wire.  Resistance reads 1.1-1.2 ohm between the three of them.  Manual says .41-.51 is the specified resistance.  Going all 5 terminals to ground I get no reading (multimeter manual says when the input is at open circuit the figure "1" will be displayed for the overrange condition).  I think that's what I want, not quite sure on the 5 terminals to ground.

For resistance measurements this small you need to place the meter probe tips together and then subtract the reading on the display from future measurements on this scale.  Your test leads have a small resistance on their own.

Tested the continuity rotor, got a resistance reading of .5 ohm between the two slip rings.  (Book says .4-.5 ohms is good).  Checked between the slip rings and center core (do I need to remove the bolt securing the rotor to test this?  If so I did not test this correctly.  The center core sticks out slightly so I just prodded it with the multimeter with the bolt in.)  Multimeter showed no reading (the "1"), so overrange which I'm assuming is infinity.  If I did this correctly I think the rotor checked out.

Your book is wrong.  Or, you misplaced a decimal point.  The rotor should read between 4 and 5 whole ohms.  0.5 ohms shows a nearly shorted rotor needing replacement.

For the voltage regulator/rectifier I got no reading for every test I did.  Green to the three yellows and reversed, as well as red/white to yellow.

The rectifier needs a special scale selection to place enough voltage on the diode to activate it.  Looks something like this   -|>-

So, from my limited knowledge and experience (practically zero) it appears to me that my regulator/rectifier may be toast.  Hopefully I can get some of you resident experts to either confirm or deny this.

The regulator may indeed be bad.  If the rotor has this low a resistance it will draw lots of current through the regulator.  This may or may not damage it with this overload.  You'll need to test its output when presented with the proper r4-5 ohms on it's output.  It should have whatever low battery voltage there is on its output.  If not, THEN it's toast.

Thanks tons.

I did not know that about the charged battery, I'll remember that for next time.  I did do the reading right after charging it.

My multimeter has a resistance of .2 ohms, so I guess the resistance was .9-1.0, still slightly higher than my manual says.

The manual says this about testing the rotor and I quote, "Use an ohmmeter and check for continuity between the 2 slip rings.  There is no factory specified resistance; some resistance should be present but it should be very low (approximately 0.40-0.50 ohms)."  Manual is Clymer Honda CB650 Fours 1979-1981, came with the bike.

I'm not sure what you mean about special scale selection.  On the multimeter?


So in essence my rotor is most likely toasted.  Yay.  Very common issue from what I've read about these bikes.  And I can't properly test the r/r until I have a working rotor.

There are a few rotors floating around on eBay for $150 each, is there any place that will re-wind them for less?  I'm assuming if I go pull one off a bike at a salvage shop I'll have pretty much the same issue either soon or down the road.

Thanks for the help!

[Hush]

Forum member "Kit" is having hers rewound right now for her CB650, she will have the costs you need.
I paid $50 in sleepy ole New Zealand for a rotor so $150 US would be way too much.


Quote from Kit:  The guy got them on the 6th and he advertises 1-3 day turnaround time for just the rotors.  (However, I'd expect longer since he takes the core, unwraps it, sand blasts it, cleans it up, rewinds/rewires) so I dropped him an email today.

Here is Kits' thread...http://forums.sohc4.net/index.php?topic=30602.0

[TwoTired]

My multimeter has a resistance of .2 ohms, so I guess the resistance was .9-1.0, still slightly higher than my manual says.

Maybe.  Measuring resistances this small is something of an art.  I suppose I should have warned you that each meter has a measurement error specification.  They aren't perfect, so you have to add that variable into the measurement, too.
I wouldn't worry about your stator, though.

The manual says this about testing the rotor and I quote, "Use an ohmmeter and check for continuity between the 2 slip rings.  There is no factory specified resistance; some resistance should be present but it should be very low (approximately 0.40-0.50 ohms)."  Manual is Clymer Honda CB650 Fours 1979-1981, came with the bike.

You can believe Clymer if you want.  But, here is the math.  One of the staples of electrical work is ohm's law.  E = IxR  or I = E/R.  I is current, E is voltage, and R is resistance.
The regulator supplies the rotor with battery power when it needs charging.  Lets say that's 12 V.  If the rotor were indeed 0.5 ohms, and we use the equation to calculate current, then you see that the rotor would attempt to draw 24 amps through the regulator and out of the battery, (if the regulator is capable of surviving that current draw).  Let's say the alternator's rating is 200 Watts.  Using Watt's Law, P = I x E, and assuming the alternator delivers 12 V to the battery, the alternator is capable (when working properly) of delivering 16.67 Amps to the entire bike, maximum, when revved to 5000 RPM.

You might want to drop Clymer a note and ask what alternate reality they are using their physics equations from.

The rotor in your alternator is it's field coil electromagnet, whose magnetic strength and spinning RPM determine it output.  The 350, 400, 500, 550 and 750 use a similar electrical design, except the Field coil is stationary.  They have a specified resistance of 4.9 ohms (or 6.8 ohms for the 750).  Let's apply the same math as above.  12V @ 5 ohms draws. 2.4 amps.    The alternator is rated at 150 W, so it can put out about 12.5 Amps, leaving about 10 amps to run the bike. (These are ballpark figures)
750 is better at making power 12V @ 6.8 ohms is only about 1.7 Amps for the field draw and it's 210 watt alternator.  So, there is 17.5 amps to run that bike.

You still think the Clymer is a reliable source?

I'm not sure what you mean about special scale selection.  On the multimeter?

Yes, almost all Multimeters have a function knob on them to select operating mode and or/ scale.  Post a pic of yours, and I'll tell you if it can make diode measurements.

So in essence my rotor is most likely toasted.  Yay.  Very common issue from what I've read about these bikes.  And I can't properly test the r/r until I have a working rotor.

You can test the regulator with a 5 ohm 30W resistor, and your voltmeter. 

[Modest_Man]

My multimeter has a resistance of .2 ohms, so I guess the resistance was .9-1.0, still slightly higher than my manual says.

Maybe.  Measuring resistances this small is something of an art.  I suppose I should have warned you that each meter has a measurement error specification.  They aren't perfect, so you have to add that variable into the measurement, too.
I wouldn't worry about your stator, though.

The manual says this about testing the rotor and I quote, "Use an ohmmeter and check for continuity between the 2 slip rings.  There is no factory specified resistance; some resistance should be present but it should be very low (approximately 0.40-0.50 ohms)."  Manual is Clymer Honda CB650 Fours 1979-1981, came with the bike.

You can believe Clymer if you want.  But, here is the math.  One of the staples of electrical work is ohm's law.  E = IxR  or I = E/R.  I is current, E is voltage, and R is resistance.
The regulator supplies the rotor with battery power when it needs charging.  Lets say that's 12 V.  If the rotor were indeed 0.5 ohms, and we use the equation to calculate current, then you see that the rotor would attempt to draw 24 amps through the regulator and out of the battery, (if the regulator is capable of surviving that current draw).  Let's say the alternator's rating is 200 Watts.  Using Watt's Law, P = I x E, and assuming the alternator delivers 12 V to the battery, the alternator is capable (when working properly) of delivering 16.67 Amps to the entire bike, maximum, when revved to 5000 RPM.

You might want to drop Clymer a note and ask what alternate reality they are using their physics equations from.

The rotor in your alternator is it's field coil electromagnet, whose magnetic strength and spinning RPM determine it output.  The 350, 400, 500, 550 and 750 use a similar electrical design, except the Field coil is stationary.  They have a specified resistance of 4.9 ohms (or 6.8 ohms for the 750).  Let's apply the same math as above.  12V @ 5 ohms draws. 2.4 amps.    The alternator is rated at 150 W, so it can put out about 12.5 Amps, leaving about 10 amps to run the bike. (These are ballpark figures)
750 is better at making power 12V @ 6.8 ohms is only about 1.7 Amps for the field draw and it's 210 watt alternator.  So, there is 17.5 amps to run that bike.

You still think the Clymer is a reliable source?

I'm not sure what you mean about special scale selection.  On the multimeter?

Yes, almost all Multimeters have a function knob on them to select operating mode and or/ scale.  Post a pic of yours, and I'll tell you if it can make diode measurements.

So in essence my rotor is most likely toasted.  Yay.  Very common issue from what I've read about these bikes.  And I can't properly test the r/r until I have a working rotor.

You can test the regulator with a 5 ohm 30W resistor, and your voltmeter. 

I wasn't trying to say the book was right and you were wrong, it's just pretty funny that the repair manual is off by a factor of 10.  I vaguely recall bits and pieces about Ohm's law and Watt's law from college physics.

Here's a very terrible cell phone shot of my multimeter knob.  I'm assuming you mean the 2k ohm setting, which has an odd little symbol next to it.  If you can even make it out.



There is a rebuild up on eBay now for $69.99  eBay, and I'm reading through the 50 page topic that Hush linked me too.  Thanks.

[Duke McDukiedook]

That 2K Ohm setting looks like the diode tester.

Wiring schematics and books are wrong all the time, when I was rebuilding my old Harman Hardon Citation tube pre-amps and amp they had the wrong resistors labeled in certain point in the diagram. Wrong resistors in the wrong place can get very expensive when you have NOS tubes in there!

[TwoTired]

Yes, use the 2K setting on the omega scale to measure diode integrity. 
It will place enough voltage into the circuit under test to forward bias and stimulate a diode into conduction.  Without that voltage, even good diodes will appear to be open circuit with both polarities.

You might think the manual being wrong is funny.  But, I find instructional manuals that have such errors as despicable.  Especially when such glaring errors aren't corrected in successive edition printings.  It's gotten so that I don't believe much of what Clymer prints, unless I find it in a more reliable manual first, like a Honda manual.  And, then that begs the question about Clymer value in the first place.
Clymer seems to be more interested in marketing and sales, than distributing reliable information, which I give a big fat FAIL to, as a reference and instructional book offering.
Yes, I have Clymer manuals.  They are the last ones I look at, only to confirm what I already know, mostly.

Cheers,

[scunny]

don't quote me but I thought the resistance between the slip rings was 4to6 ohms

[Hush]

Yeah it's about that Scunny and yes you can check the slip ring to centre bolt while it's on the bike.
You are simply tetsing to see if either of the copper rings is making contact with the bike which they shouldn't as that will screw up your charging.

[Spanner 1]

" Low grade copper supplied to Honda Motor Company makes for failed rotor windings 1980,1981( at least ) ", read all about it ! "
IMO....worst thing about Honda bikes early 80's is the bad rotors....

[Frankenkit]

Hey, Hush, you're more on top of things than I am!

Another odd thing of note, my rotor read 4.1-4.5, which is on the low side of spec, but still spec.  I think that's pretty similar to Hush's readings, too... which makes me suspect Honda's opinion of 'spec' but that's another thing.

 Still, I know I have two or three good starts out of the bike.  One once the bike is taken off the charger in the morning, maybe one if I need to restart the bike on the way into work, but it turns over verrry slowly, and another slightly peppier, but still not quite there start at the end of the day. This is riding at 5-7k rpms for half an hour, where it should definitely be charging.  I think I left all the appropriate info on the thread, the only difference being that I've been riding quite a bit since then.  No improvement, and odds are against me starting again when I'm running high beams, too.

You don't necessarily need a special tool to get the rotor off, either.  I tried the rear axle trick, but after it started seeming like it was going to damage the threads on the rotor, which wasn't optimal. I went out to Ace Hardware and got a 3ish inch long 18 mm bolt (metric, every inch of the way: and with MickeyX tightening down the bolt and me on the other side with a 23 socket on the crank shaft, we popped the bugger off.

[Hush]

hadn't started my bike in over a week Kit, went out to shed today and broommmmmm first push  I'm a happy camper since I changed out that old rotor.
My old rotor still tests out fine too?

[Modest_Man]

I should have a re-built rotor in the mail soon.  Hopefully that takes care of it, but I think I'll swap out the r/r at the same time for a digital one (probably try making my own).  Wouldn't want to fry a second rotor due to a faulty r/r.

[Hush]

One of our forum members makes a reg/rec for our bikes.
Contact "Pinhead" here's his link:  http://forums.sohc4.net/index.php?topic=12465.0

[Frankenkit]

I invested in one from oregonmotorcycleparts.com because the guy's local to me and sends a sweet looking unit with all new connectors, etc etc. 

[Modest_Man]

I'll take cheap over sweet looking any day!   

I've read that thread over twice already, and have the part numbers lined up Hush.  Thanks.

[Pinhead]

You won't be disappointed using the Ford regulator; my bike charges at 14.5v at 1500rpm and beyond. I haven't replaced my battery since I installed the regulator 3 years ago and it's showing no signs of heading south.

[TwoTired]

I should have a re-built rotor in the mail soon.  Hopefully that takes care of it, but I think I'll swap out the r/r at the same time for a digital one (probably try making my own).  Wouldn't want to fry a second rotor due to a faulty r/r.

I think that risk is pretty small.  The regulator can only pass voltages from zero to max battery voltage.  Normally, it would pass the full battery voltage only when the battery is low, like below 12.6 V.  So the rotor is designed to take that indefinitely.  The math is applied to a 5 ohm rotor suppled with 12.6 V which then draws 2.5 amps or about 32 watts.  I expect there is some margin in there as the circuit is only protected by the main fuse.  I'd guess that even 40 watts indefiniely will not harm an otherwise good rotor.
So, if the regulator fails open, there is no worry for the rotor as it is getting zero volts and no watts (or heat) is generated by the rotor windings.  But, let's say the Regulator fails shorted, input to output passing full battery voltage.  This would allow the alternator to make max power and charge the battery even when it is full.  The voltage could climb to 15, maybe 16 volts (if you aren't monitoring it with the DVM).  The rotor winding resistance is the same 5 Ohms, but now fed with 16 V, it draws 3.2 amps or 51 watts.  Maybe if you did this over a long duration it could hurt the rotor.  But, surely you'll test the system when you put it back together.  Begin with a fully charged battery (and your new rotor) and watch the battery voltage when revving the engine over 4000 RPM-ish.  If the battery isn't charging (increasing it's voltage) the regulator is suspect.  If the battery voltage slowly climbs over 14.8 to 15V, the regulator is suspect, discontinue testing and your rotor should be at very minimal risk if you only allow this to occur for a minute or two.  But, now you will have knowledge about whether you regulator is functioning properly, or not.

Cheers,

[Modest_Man]

Great info, thanks.  I'll let you guys know what happens after I get my "new" rotor.