Topic: CB550K Charging Issues, help needed!

[Orange550]

Hi all, I have a '75 CB550K that has some charging issues that I can't seem to get sorted out. The problem I have, is that the battery is being OVER-charged, which seems to be at the opposite end of the problem spectrum for most people.

I've cooked two batteries and after replacing the REG/REC with a new one from Rick's Motorsports, it's still over charging. While running and under power (3K or so on the tach) the multimeter readout slowly climbs to 15+ Volts before I shut the bike off in fear of destroying another battery.

I replaced the stator with an identitical stock used part off another CB550. 

I'm wondering if this could be an issue with the field coil? I've measured it at 4.8 Ohms. The guy at Rick's told me they should be around 7 Ohms. Could it be weak and overcharging to compensate? Any help is greatly apprecitated!

[scottly]

The 750 field is about 7 ohms, but the 550 field is about 5 ohms, so that's not an issue. What voltage do you read at the black regulator wire, with the key on and motor not running? Place the meter red lead on the battery + post, and the meter black lead on the reg black wire, and post your results.

[hsas.69]

I would say scottly is right on. The regulator is seeing lower than true battery coltage on the sensing wire.

Sent from my LGUS992 using Tapatalk

[Orange550]

Thanks for the input. I did as Scottly suggest, here the results
Battery - across terminals - 12.8V
Black wire 12.8V - key on - neg meter lead on black reg wire, red meter on battery +.
   Actually, I'm getting 12.8V with key off too - is this proper?

Also, used toubleshooting instuctions which came with reg/rec from Ricks MS.
    Disconnect R/R from harness. Turn key ON. Test voltage of the black wire (harness side). Should not be more than a 0.4 VDC difference between this - and the batttery posts. Mine showed 12.8V - no drop.

Thanks for the help!

[Orange550]

CORRECTION ....

I think I tested Scottly's suggestion wrong. I had the reg rec black wire disconnected from harness when I tested and got 12.8V. (I was testing the black wire from reg/rec)

This time, I left the wires connected and got 1.25V (1.20-1.25V) when putting meter probe into blade connector, with key ON.

Is 1.25V a  problem?

Thanks again!

[Orange550]

Thanks Cal.
I actually rewired the bike, used 'Vintage Connections' bullet connectors and block terminals. All wires have good continuity.

You say, "should notice an improvement" after checking/cleaning connections.
    What should I be seeing? Zero?

Does this give any indication of a bad reg/rec? I spoke with Rick's and they were quick to offer an excange saying it could be a bad one. But, they were also who told me the field coil should be 7.0 ohm - (Scottly says it should be 5.0. I have 4.

Thanks

[hsas.69]

Is that what the meter read or what the difference was?

Sent from my LGUS992 using Tapatalk

[Orange550]

1.25V is what the meter read - and it was dropping with the key on.

Calj - I have not checked resistance between black and red from the key. I'm not sure of what you're refering. Can you explain this test.

[scottly]

You have a 1.25 volt drop between the battery + terminal and the black wire that feeds the regulator, instead of the .4 volt drop Rick's recommends. In reality, .5 volt is a more reasonable expectation. Your field coil at 4.8 ohms is well within the factory spec of 4.9 ohms, +/- 10%.
Test for the voltage drop at the junction of the red wire at the ignition switch, with the switch connected and the key turned on, and post your results.

[Orange550]

Scottly - if I understood you correctly, I tested the battery across terminals and got 12.4 VDC this morning - then removed positive meter lead from battery and placed on RED solder joint behind ignition switch and got 11.3 VDC and dropping, with key ON. (same reading as battery, with key off)

Is this what you meant?

[Bodi]

1.1V drop is way too much between battery + and the red wire at the ignition switch. Guessing normal load with lights and ignition at around 7A, that's 7.7W of heat going somewhere... sounds like "not much", but actually enough to easily melt the solder connections behind the fuse clips or damage a bullet connector beyond salvation.
It's best to measure voltage drop rather than actual voltage - the battery voltage will drop whenever the key is ON, confusing your measurements, since the load from lighting and coils is fairly high. Put one lead on battery + and the other on the point you want to measure drop at. The switch red should be close to zero drop - maybe 0.2V max under load. To the regulator black wire (connected to the regulator!) you should have 0.5V or less. If that's not possible even with clean/tight harness connectors and a known good fuseblock... consider adding a relay activated by the black wire, switching power directly from battery + (but have a fuse in the feed!!! - 5A would be good) to the regulator power input. The regulator needs a reference voltage as close as possible to the actual battery voltage in order to work properly!
That drop is in not much wire in the harness, the fuseblock connector, fuse clips, and the MAIN fuse: there's nothing else between battery + and that red wire.
The fuseblock is a common problem, the plating on the clips will have disappeared in 30+ years and the metal surface now prone to corrosion. The ideal fix is to replace it with a minifuse model, drop-in ones are available that fit the old mounting and have the connector attached.
The fuseblock connector also ages poorly. The spade terminals can be cleaned and the females tightened.
The wire is, well, just wire. Unless the insulation was damaged or a bit was overflexed and the metal damaged, the copper inside will be shiny and unchanged (except near connections where oxygen gets in at the copper through the stripped end... but the oxidation just makes soldering difficult and doesn't affect conductivity, unless so severe the wire looks to have green fur.

[Orange550]

thanks Bodi, this is a very good explanation.

The voltage drop on the Red wire at ignition switch is 0.85V - key on - measured as you describe with one lead on battery + and the other at the switch Red.

Voltage drop at the reg/rec Black wire is 0.85V - key on - reg/rec connected.

So what causes the voltage drop? Bad ground? Bad connections? Is it just somewhere in the circuit that the voltage is 'leaking' somewhere? I hear what you say about the fuse block. I have one ordered and will change that out first and re-test, before I send the RR back to Ricks. 

Thanks for all the help!

[Deltarider]

Repeat measuring if possible with engine running and please report back.

[b52bombardier1]

For Orange550,

The resistance creeps in a lot of places. Oxide on the various connectors is probably a large source. The key switch electrical contacts live in a harsh environment that is open to dirt and other contamination. The switch contacts are also subject to physical wear with turning on and off. People also like to spray oily lubricants down the key hole which attracts dirt - electrical contact cleaner is better here.

Another thing is your wire insulation at the connector can look great but you could be hanging on by one copper wire strand internally.  This is a frustrating situation because that connection will easily pass a low amperage continuity check on a multimeter thus deceiving you.

And this is all doubly worse on my six volt bikes below. Ohms Law deals very harshly with these bikes when it comes to extra resistance in the wiring which means grounding and the replacement of suspicious connectors gets a lot of attention.

Rick

Sent from my SAMSUNG-SM-N900A using Tapatalk

[Spanner 1]

Bodi is boss with his explanation , also follow the main ground from battery to frame engine bolt connection and undo the nut and remove the bolt, shine up the ring terminal on the wire, file the frame 'tube' end shiny and re-install. The connections at the battery are shiny and tight, right ?

[scottly]

The voltage drop on the Red wire at ignition switch is 0.85V - key on - measured as you describe with one lead on battery + and the other at the switch Red.

Voltage drop at the reg/rec Black wire is 0.85V - key on - reg/rec connected.

So what causes the voltage drop?

Since you are measuring the drop between the battery + post and the red and black wires, the ground is not involved; that is a different test.
Since you get the same voltage drop on both sides of the ignition switch, the switch is good, and the drop is between the switch and the battery. The most likely suspect is the fuse box.