Topic: Electrical Problem on CB650

[CBJoe]

I have a 80' cb650C that started having an electrical problem when I was preping the bike this spring.  I've been busy so i'm just now getting to it...... 

When I turn the ignition switch to ON, the headlight is really dimmed (kind of like the circuit's being over loaded) and the 30A(?) fuse on the starter solenoid with smoke. I've ruled out most of the wiring, the rectifier, condensors, and the starter solenoid.  About every 10 attempts, the bike will start with no problem. 

Does this sould like a short in the starter? or could it possibly be the alternator?  I have two parts bikes to pull stuff from, i'm just trying to save some trouble.

Thanks for the help.

Joe

[byidesign]

Sounds like the relay going bad,or too much starter draw...
    if you disconnect the starter from it{relay}
        is it OK? , or still smoke fuse?
       If you {be sure it's in neutral}
        jump the {hot}starter wire right from the battery
         while disconnected from relay, does the starter itself
           work correctly........?
                   Post results.......
                         bruce
             

[razor02097]

wait does the headlight dim only when you press the starter button or does it dim when you click the ignition to ON?  Starters do go bad if they get too hot when they go bad like this they draw massive amounts of power and produce little results.  If you jump the solenoid and still get a slow crank then the armature probably fried in the starter... you can confirm this if you take the starter out and it reeks of burnt wiring.

[gasguzler]

I know very little about this but I just wanted to jump in and say my '79 cb650 starts very well, but the headlight does always dim when I hit the starter. So that's not necessarily a sign of a real problem, it would seem to me (the other stuff would be).

[CBJoe]

When this occurs, the headlight dims when I turn the ingnition to the on position.  I have two parts bikes in the garage, so i'm going to try and test/swap the starter.  I've already tried a different ignition.   I'll post my findings, unless i run out of fuses.

joe

[Ibsen]

Have you taken off and cleaned the battery terminals, the ground wire terminal on the frame for the battery ground cable, and the connectors on the starter relay and the 30Amp main fuse? It sounds to me that there is a bad, or loose connection somewhere, and a bad connection means an increased resistance, and production of heat.

[CBJoe]

The battery terminals are clean as well as the connections on the starter relay/solenoid.  I attempted what "byidesign" suggested by hooking up the hot terminal of the starter directly to the battery and the starter sees to be fine. Just in case, i pulled a starter off of one of my parts bikes and installed it.  The problem seemed to be fixed for a little bit (10 Minutes of fiddling), but then the 30A fuse blew again.

Is there a good way for bench testing the starter relay to see if is good or bad?  I have two other starter relays off of my parts bikes but they both seem to blow the 30A fuse as well.  They are both as old and used as my relay though, so they could all be bad, but i doubt it.

Could the alternator be causing this? Even though the problem happens before the bike is started?

To clarify:

1 the fuse blows when the ignition switch is turned on.  NOT when the starter button is pushed. 
2 It doesnt seem to matter if the thumb switch is in the on or off position. 

Thanks for all of the help.

[techy5025]

The thumb switch, in the stop position, completely disconnects the points/ignition from the battery
and fuse. If you are blowing fuses in this position, its not the ignition system causing it.

A possible problem might be the alternator diode bridge....try unplugging it and see if the fuse blows.
If not, then maybe you have a short in one or more of the diodes in the bridge.

I doubt if the starter relay has anything to do with your problem unless there is an internal short from
the relay solenoid winding to ground.....highly doubtful especially if you have switched it out.

Do you have a schematic of the wiring of the bike.  That would be helpful to use in troubleshooting.
An "almost have" for old bikes.

Jim

[Ibsen]

Then I tend to agree with techy5025. There are three wires connected to the main fuse. One from the battery, and on the other side of the fuse one to the ignition switch, and one to the regulator/rectifer unit. Your problem wil most likely be with either one of these wires, the ignition switch, or the reg/rec unit.

This is the wiring diagram for your bike:

CB650 WIRING DIAGRAM

[Short Round]

The problem sounds like it may be the rectifier not converting the DC into AC proplerly.  the dimmed light are prob due to the lack odf AC current to the lights, ect.  Try switching it out with another one if you have one off of your parts bikes and let me know what happens.  Email at Littleitaly52@hotmail.com, if that s not it I will ask a few of my riding buddys and see what they think, one of them is and electrical guru

[CBJoe]

Well, currently i'm out of fuses.  I'll have to run to the bike shop tomorrow for a pack.  Thanks for all of the input, i'll post results as soon as I do more testing (probably not till sunday due to attending a friends wedding).

later

[CBJoe]

OK.... i'm confused.

The manual refers to taking resistance readings on the regulator/rectifier.  I have 3 regulators.  1 from a 80 650C and two from 1981 CB650C's.  There are different testing methods between the 80' and 81's.  Are these regulators interchangable between years??

Also, All three seem to be failing the tests between the manual.

It says i'm supposed to measure resistance between the green wire and each of the yellow wires.  All readings should be the same and either a high resistance (>2000kohms) or a low resistance (5-40ohms).  When the leads are swapped the readings should be oppisite from before.

I'm getting appx 2Mohms one way and infinite when the leads are swapped.   Could i be doing something wrong??  I cant believe that all three regulator/rectifiers are bad ( but i suppose when they're all 25years old anythings possible)

[TwoTired]

If you are using a digital meter, you must use a special scale to measure the diodes in the rectifier.  Use the scale marked
--|>-- for measuring diodes.

Why?
Meters inject some of their power in the circuit under test, for a small current flow.  Their display is a measurement of the power not consumed by the circuit, infering resistance.
Newer meters inject so little power that their is not enough to make silicon devices conduct  This can be VERY helpfull in troubleshooting some ciruits.
The special scale selection supplies extra power to the circuit so that silicon devices WILL conduct when given enough power with the right polarity.  This is VERY usefull for determining that their basic function is intact.

cheers,

[Ibsen]

I don't know which manual you have, but this is from the Honda workshop manual for the European model:

VOLTAGE REG/REC TEST

I don't have any of my 650 manuals available here at work, so I can't tell if there is any difference between the models though.

[CBJoe]

OK..... i think i was just smacked in the face by one of those obvious tests that could have saved me much trouble and anger.

I cant completely verify it until i get more fuses. but the problem seems to be my alternator.   I followed the manual (who'd of thought about that) and measured the continuity between the wires, per the manual.

I have a short between the black and white wires, they read about 20-30 ohms.  It is supposed to be infinite.  It's a good thing i have those parts bikes.  Thanks for all of the help and i'll post my results on sunday.

regards

[CBJoe]

I think that if i didn't just piss off the neighborhood (4-1 style) then I've moved to the right place.   

The alternator was definitely the problem.  I just fired the bike up with no burning fuse death smoke and it purred like a pissed off kitten.

I haven't heard the bike run since April so I was jumping up and down in the alley like a fool.  By the way, i found a 30A fuse on my junker GL1100 which gave me one last chance at hearing it run. 

Thanks for all of the help... I'll have to post pics as soon as i get it put all back together.  Hopefully a family of mice hasn't taken up residence in my helmet, since I'll have a reason to wear it until now. 

[cb650]

Just dont eat the raisins .




                  Terry

[Ibsen]

 

Sounds good.

Btw, according to the workshop manual that I have, the reg/rec units are simulare for the 79-80 and 81-82 models. It's the test procedure that changed. For the early models they recommend using an ordinary multimeter set to ohm range, for the later models you should use an ohm meter with a reversed polarity(+ as ground). I think that's why your measurements didn't match the table.

[CBJoe]

I spoke with one of the engineers at work (he's a kawasaki guy) who informed me that newer multi-meters wont produce the same measurements as the older analog ones when it comes to the specific test the manual refers to.  I believe that "twotired" stated something along these lines earlier.  I guest the good thing is that I have two extra rectifiers. 

 

[Ibsen]

And I believe they are right about that. I have had some strange results sometimes when I have been using a modern digital multimeter.