Topic: 73 cb 500 electrical issues

[the dark]

Greetings and salutations,

 here is the scenario:

  Bike was running very well after tune-up, carb clean/synch, some troubleshooting for an oil leak (countershaft) and other stuff.... in any case was having a blast and came to a stop light and the bike just up and quit. Both the tail light and head light went out, so immediately I knew I was electrical. I have since pulled the entire harness from the bike, checked/cleaned all the connections, did some repair of a POs " handiwork" and reinstalled the harness, turned the ignition on....and nothing. Ive tried to test the rectifier, regulator and stator, field coil but cant get any readings, both in circuit and out. soo......Help??

i am running a pretty slimmed down cafe system, no signals, no bar switches, ect.

its beautiful out, I need to ride.

 Thanks!!

[Spanner 1]

On my '70 bike the ignition switch did just that, died and never came back to life..!
I bet your ignition switch is the org. '73 vintage....did you test it ?
RED into switch always' hot': BLACK coming out 'hot' when switched ON.....take a close look at your fuse and holder too.

[the dark]

pulled the ingnition apart touched the wires...nothing, fuse seems good, going to get another few to test, and ive got a 30a holder for the plastic square fuses instaed of the original 3 10a glass. dont imagine this makes any difference to my particular setup, but it may...

checked the battery out of curiosity, only at 10v which means battery replace ..but it should still be plenty to turn on my tailight, dimly at least...but still nothing.

the low battery has me thinking rect/reg again...bargh. maybe i'm shorting or grounding somewhere? but that would be a slow loss of power, not dead on the spot?

[TwoTired]

At 10 V the battery is totally depleted and needs to be recharged.  After charging, THEN test for proper battery voltage.

Once you know you have a good, fully charged battery, THEN you check the charging system to see if it will maintain the battery at full charge.

Do you have a multimeter?  Do you know how to use it?

What guides are you using for troubleshooting?

The coils multiply the battery voltage to get spark.  It's a ratio. When the battery voltage gets too low, the coils can make enough voltage for spark.

The alternator does not charge the battery at idle (assuming the lights are on.)  In fact, the bike uses more power than the alternator can make at idle.  What the alternator doesn't make comes from the battery, if it still has a charge left.

[Celco]

Its happened to me a few times now... But change the fuses.  The old ones that I had in my bike (and under the seat) would get hot enough over time but not burn the filament.  The actual capped ends would come loose because of the vibes and the heat.

Test it out, you might find something.

[the dark]

thanks,

I do have a multimeter, but its just a cheap one, will charge the battery to full and recheck the test list from the manual tomorrow.

Correct me if I am wrong but shouldn't I be able to test the resistance of the stator, field coil, rectifier and regulator w/o a battery? that is what has me stumped, no readings on anything, unless I'm being totally daft and using the meter incorrectly.

will also triple check the fuse and fuse holder and wires thereunto.

[DavePhipps]

Here's link to a guide to help you the the troubleshooting.

http://www.electrosport.com/technical-resources/library/diagnosis/fault-finding-guide.php

It's a pretty good guide. I've had to use it a few times and it helped a lot.

[TwoTired]

Correct me if I am wrong but shouldn't I be able to test the resistance of the stator, field coil, rectifier and regulator w/o a battery? that is what has me stumped, no readings on anything, unless I'm being totally daft and using the meter incorrectly.

Yes, you should be able to measure resistance w/o the bike's battery.  The meter has it's own battery to power the circuits being tested.

Does the meter make a reading the with the probe tips touched together?

There are lot's of meter brands/styles.  If you you need help with yours specifically, you'll have to tell which you have.  Or, maybe post a pic of it.

[the dark]

well..this is interesting...bought a new meter, set it to battery load test 12v to test the battery and it actually read 12.2v, without the bike running. Thanks davephipps for the link, looks very useful if I can start the bike, but right now its just a tease!

 Will test the resistance of the r/r, stator, field coil ect again with the new meter and post my results.

 Thanks so much for the insight, I was a bit boggled earlier.

[TwoTired]

A fully charged wet cell battery should read 12.6-12.8V (static) after a two hour rest off the charger.

[Bill/BentON Racing]

It sounda like your problem is in your ignition system,worry about charging system after you get running,make sure battery is 12v +,and replace or check those fuses,red hot all the time 12v,blk is switched hot ,12v w/key on,make sure you have 12v to switch,,key on check to find where you lose the 12v after ignition switch,check your grounds also.As someone said very easy to bypass switch,hook red to blk.do you still have kill switch,12v @ coils?,stock pts plate? Check your wire connectors in headlight ,Good Luck,Bill

[the dark]

Problem Solved!!

It was faulty soldering at the ignition switch. Looked OK from the outside but....no contact/current. So YAAY! Now I can run through the charging system! Or maybe go for a bit of a tear and do it later tonight...

 Thank you guys so much, this is my first bike since I was 18, purchased not running with unavailable maintenance history. I have been able to do the entirety of the work myself solely by reading the posts on this forum and have learned an extraordinary amount in the process. I would buy you all a some beer if you lived in Vancouver, but alas...

will post some pics later today, its a bit of a rat but goes like the dickens with the subtlest twist of the wrist.