Topic: Field and Stator coil question

[NickC]

1975 CB550k

What would cause both to go bad? I've had a charging problem since my rebuild. Regulator, good. Rectifier, good. Tested the  2 wires on the field coil- 0.00ohms. Damn, moved over to the Stator coil. All 3 yellow wires, 0.00 ohms. What causes these things to go bad? This bike only has about 18k on it, but has seen somewhat of a rough life.

[TwoTired]

The stator windings are normally 0.35 Ω +/- 10%.  What did you expect?
What is the accuracy of your test equipment?

The simple fact that all your readings indicate 0.00, makes me question either test equipment or test technique.

But...
What would make them both go to a true 0.00 Ω ?   Mechanical mayhem.  Sledge hammer, blunt force trauma.  A really hot fire, like a smelting furnace. Localized interruptions in physical laws (perhaps from an alternate universe).  A vivid imagination.  Or, the introduction of mind altering substances making those readings seem real.

But, I'm just guessing....

[Hush]

I'm with TT on the way you may have tested your components, however being one of those replace and see guys (as testing bores me to death) find another rotor and put it in, worked for a few 650's I know of.
Do 550's have rotors?
Anyhow the standard test for those large hunks of metal are not accurate and often show a rotor to be good when usefull only as a doorstop......replace.....get back riding.

[dave500]

digital multimeter?touch the probes together and you should get a reading if the meter is ok,if theyre gone theyre gone.,clean connections as you test?is it on the correct setting ,ie not volts or amps?

[NickC]

I'm using a brand new fluke multi-meter. Yes, I'm using it correctly. Done some other checks, and even compared it to my old fluke with the same results.
Testing the field coil- Check resistance between both wires
Testing the Stator- check resistance between all 3 yellow wires.
This is correct, no?

[TwoTired]

What is the scale reading when you touch the probe tips together?  (Wires, have resistance, too.)
Can you make any resistance measurements (anywhere) to show the meter is capable giving a non-zero indication?

It is really only more expensive, purpose built, ohmmeters that have the capability to measure 0.35 ohms with reliable accuracy.

The upshot is that we have doubts as to the accuracy of the numbers you've reported.
However, if you trust the measurements you've relayed, then go ahead and replace all those components. 

You might want to describe where, exactly, you are placing the probe tips for those measurements.  All the measurements are intended to be taken on specimens disconnected from the bike's wire harness, of course.

[NickC]

Ok, broke out my Ideal meter. Got about ~.08 touching the probes.
Field coil came out to 5.0 -standard resistance is 4.9+/- 10%........ good to go
Stator coil came to 1.5  -standard resistance is .35 +/- 10%......why so high?

[scottly]

You should also take readings to verify there is NO continuity from any of the leads to ground, both the field and the stator.

[TwoTired]

Stator coil came to 1.5  -standard resistance is .35 +/- 10%......why so high?

Probably test technique.  There is small resistance between probe tip and tested device contact, and it adds up. What reading do you get when both probe tips make contact either side of a single stator terminal?  Notice how that changes with the probe tip contact pressure applied?  You are poking through a resistive film on the contact.  Pointier probe tips can help pierce the film.

Now you know why terminals need to be cleaned and protected from atmospheric corrosive elements.

[Spanner 1]

Nick, the first test of your charging system should be the old ' voltage-vs.-r.p.m. ' test..... just connect your voltage meter across the battery and note the voltage, then turn ign. 'on' and start the bike...then see if the voltage rises with increasing r.p.m. up to a max of about 14.5v @ say, 5,000 rpm............ have ya tried that ?

[Hondell]

Unless your Fluke is a four wire ohmmeter you will NOT measure low resistance accurately.

[NickC]

Nick, the first test of your charging system should be the old ' voltage-vs.-r.p.m. ' test..... just connect your voltage meter across the battery and note the voltage, then turn ign. 'on' and start the bike...then see if the voltage rises with increasing r.p.m. up to a max of about 14.5v @ say, 5,000 rpm............ have ya tried that ?

Haven't been able to do that yet, had to change over to a working tach. That will be the first thing I do whenever it's back together

[NickC]

Nick, the first test of your charging system should be the old ' voltage-vs.-r.p.m. ' test..... just connect your voltage meter across the battery and note the voltage, then turn ign. 'on' and start the bike...then see if the voltage rises with increasing r.p.m. up to a max of about 14.5v @ say, 5,000 rpm............ have ya tried that ?

Damn, with a charged battery, I'm only getting 12.5, occasionally jumping up to 12.9, and down as low as 12.2

[scottly]

Hey, it's doing something if it's getting to 12.9V! It takes time to get up there to 14V, especially if you are using electric start. You've got to replace the big amps the starter takes.

[Spanner 1]

With a fresh charged battery the alt. would not kick-in until the voltage drops below say 12v... so +1 with Scottly you would not expect to see 14.5 v ..... let the headlight run ( bike not running ) until the voltage drops to say 11.5v, then start it and see if the voltage rises to 14.5v @ 5,000 rpm.

[NickC]

From my manual:
"When the battery voltage is lower than normal (less than 13.5V at the battery terminal), the current flows through the upper contact and to the field coil....when the battery terminal voltage is 12V, the field coil current is 1.6A....raises to 14v.....lowers to 0.7A"

[scottly]

It only rises to 14V After it supplies the demand of the battery, while also supplying the needs of the lights and ignition.

[NickC]

Just out of curiosity, I pulled the lighting fuses and set it at 5k, averaging 12.9, bouncing as low as 12.2

[scottly]

Bouncing while holding a steady RPM??

[NickC]

Yes, about a volt. It swings from 12.3 to 12.9, but averages in the upper range.

[scottly]

Should be steady (digital meter? not prone to vibration). Start looking for loose connections, like main chassis grounds, might also be a regulator problem. Just guessing...

[scottly]

Nick, let's get back to the basics, tomorrow. There are some questions I'd like to ask you.
Scott

[NickC]

I'm going to jump the voltage reg tomorrow, and go from there.

[scottly]

Hey, do what you want. If it was me, I would take some measurements first....

[NickC]

I tested my regulator, opened it up, checked the point gap, and the core gap. I just want to perform the "lets see what happens" trick