I think these carbs are having an ignition problem ....

[3Phase]

... Is the pegged field coil supposed to create a voltage drop? With the thing unplugged every place that should have 12v does. Plug it back in and everything loses a volt when the key is switched on. That’s what isn’t adding up for me. ...

Yes and no.

The field coil is 3.5 Ohms so with 12V to 12.9V it uses 3.4A to 3.7A and dissipates 41W to 48W of power. That is a fairly heavy load.


I'll use the tired and overused water system example:

You're in a maze of twisty passages, all alike... erm, I mean, your house is using a water system with a well and a pressure tank.

The house normally has 50 psi of water pressure, a well that refills itself at 21 gallons/minute and a 50 gallon pressure tank that can flow 10 gallons/minute (current) without losing pressure so there is little or no drama when you take a shower and someone runs the sprinklers and flushes the toilet.


But!

Someone has been flushing their toys down the toilet and playing outside in the sprinklers, seeing how far the water will go and how much water pressure (voltage) there is at every spigot in the house and the yard so the water level in the well has been lowered and the pressure tank (battery) hasn't the time or the ability to refill itself.

Because it's been run down, even with the pump running (alternator) the system cannot refill and supply 10 gpm of water and hold 50 psi, only 25 psi, maybe.

Without the pump running (key on, engine off) the pressure drops instantly when you turn on any faucet (load). Now when someone takes a shower and someone turns on the sprinklers and flushes the toilet it's instant drama!

Turn off the sprinklers and the toilet so no one can use them (unplug the field coil) and the 25 psi of water pressure seems to work for the shower again with no drama.

Allow the well and pressure tank to recharge so everything is back to 50 psi with good flow and once again you can run the sprinklers for a little while and flush the toilet before the pressure (voltage) drops.

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[Barbarosa]

LOL. I get it. Will test again with fully charged battery tomorrow.

[3Phase]

LOL. I get it. Will test again with fully charged battery tomorrow.

When you've mentioned the voltages it looked like they've been going down as you've been working. The alternator needs time or I think it's about ~20 miles to recharge the battery after one Start and yesterday you mentioned seeing 12.2V so your battery has been slowly losing its charge.

Battery state by voltage:


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[Barbarosa]

Update with fully charged battery:
12.6v at battery key off 12.4v on.
11.5 at fuse box
11.3 at ballast and coil feed
Running:
14v@2500 at fuse box
8.4v to coils (red/white) minimum changes with increased rpm
9.8 at ballast
7v at TCI (digital)

Was fixated on looking for my imaginary 9V at the coil triggers and didn't check the supply to the coils. DUH. Pretty sure they need more than 8.4v. Does this current (lol) info shed more light? And speaking of light, it takes a spell for the headlight to come on after firing up the engine.
Also, I understand Faradays theory and that voltage is discharged when the current is changed and the field collapses. That's why I was wondering about the voltage needed to make that happen. Don't see how the amount it takes to make the discharge occur matters, but it must be moot if there isn't good voltage at the coil to start with.

[Barbarosa]

Voltage testing at the fuse box was taken at the ignition lead.

[motoman]

For a voltage drop with key on, remove, take apart and clean Run/Stop switch. This connection completes the circuit.

[3Phase]

Voltage testing at the fuse box was taken at the ignition lead.

Now that the battery is charged it's only dropping down two-tenths of a Volt when the key is switched on so that's better.


It looks like you're losing a hair over a full Volt from the battery to the fuse so you have dirty connectors and/or a dirty ignition switch.

You've got even more voltage drops as you go to and through the Ballast to the coils too.

Running:
14v@2500 at fuse box

That's low but if the battery is fully charged it'll do.

8.4v to coils (red/white) minimum changes with increased rpm

14V - 8.4V is a 5.6V drop from the fuse box.
Is the engine still running? Where -- exactly -- is this voltage measured?

9.8 at ballast

14V - 9.8V is a 4.2V drop from the fuse box.
Again, is the engine still running and where -- exactly -- is this voltage measured, on the Line/Input side from the fuse box or the Load/Output side of the resistor to the ignition coils?

7v at TCI (digital)

Again, is the engine still running? 7V at the TCI... is it voltage that's just sort of hanging around the neighborhood like a general ambient voltage kind of thing or were there any specific pins/wires that you checked?



By the way, when you were checking the fuel levels in the float bowls it seemed that per your original problem of carbon fouling the spark plugs that you never did the running fuel level test, only the bench test:
Did you do the running fuel level test?

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[skids]

Barbarosa,

Put the cover back on the TCI.

The ignition coil primary voltage may seem low but it's designed to be low. The '80SG uses a 1.5 Ohm ignition ballast resistor to drop the current/voltage for the ignition coil primary winding after the engine is started so it doesn't burn up the coils.

You'll only 'see' +12V on the ignition primaries with a meter when the engine is cranking and the Start circuit is working. The White/Red wire goes hot from the TCI and feeds a junction/splice in the harness with the coil primary Red/White wire.

For the Orange and Gray wires that come from the coil primary windings and go to the TCI, they get switched on and off just like the old points and condenser (Kettering) ignition systems. When you try to measure their voltage with a digital meter it will fluctuate because you're using the old-skool 'Tach' connection and the meter is basically taking snapshots of instantaneous voltages so it acts like an erratic digital tachometer. Use an analog meter and it will stop doing that.

Unless the bike's been seriously miswired or just plain shorted out then the stator doesn't do anything until the engine is running. A fully charged battery should hold 12.6V to 12.9V so recharge the battery or replace it if it won't hold a charge.

With the ignition switch on and the engine not running, the voltage regulator has the field coil pegged wide open to raise the system voltage and recharge the battery but because the engine is not running all it can do is drain the battery. Recharge or replace the battery and quit leaving the ignition switch on or you'll eventually kill the battery.

So, if the the voltage drop you're seeing at the battery happens when the ignition switch is on but the engine is not running then it's because your battery is over half dead and doesn't have the ability to maintain the system voltage while you take measurements. Recharge or replace the battery.


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That is a very good, comprehensive explanation!

[Barbarosa]

Update on the update

Posting these values again in better detail and hoping everyone can understand what’s going on. Seems like some responses are sarcastic or condescending and I am not into wasting peoples time if they think they are dealing with an idiot. I don’t think I’m an idiot (lol debatable) and I hope that if we can figure this out maybe the next guy that starts running voltage checks will read this and be helped. That is of course if there actually is a voltage gremlin and I am not hallucinating again because they upped my dosage.

STATIC:
12.6v at battery
11.5v at fuse box (ignition)
11.3v at ballast (r/w) and coil feed (w/r) at TCI

BTW, there is 12.4v at fuse box when stator is isolated from circuit.:

RUNNING:
12.7@1000 rpm at fuse box
14v @2500 rpm at fuse box
14.8@4500 rpm at fuse box
8.4v to coils @1000 rpm (white/red on TCI) goes up to appx 11v at 5k rpm
9.8 at ballast (red/white on TCI) goes up to a bit less than 11v
7v at orange and gray wires on TCI to coils (digital meter peak voltage)

It looks like you're losing a hair over a full Volt from the battery to the fuse so you have dirty connectors and/or a dirty ignition switch.
There are no dirty connections or switches. Disassembled and cleaned. If there were faulty connections/switches I don’t believe there could ever be 12.4v at the fuse box (and everywhere else) with the stator unplugged. There is 11.3v at the TCI for the ballast and coil feed. When engine is fired up the coil feed (w/r) wire drops to 8.4v. It will increase to 11v at 5000rpm and above. Voltage didn’t do gradual climb to mirror rpms as I expected when throttled up. More like it jumped around. Snap shot effect from digital meter?
14V - 9.8V is a 4.2V drop from the fuse box. Again, is the engine still running and where -- exactly -- is this voltage measured, on the Line/Input side from the fuse box or the Load/Output side of the resistor to the ignition coils?
Engine running, both sides of ignition fuse. The 9.8v is at the ballast (r/w on the TCI) and it will also go up but does not drop when engine is started.
Again, is the engine still running? 7V at the TCI... is it voltage that's just sort of hanging around the neighborhood like a general ambient voltage kind of thing or were there any specific pins/wires that you checked?
Yep, still running. Doubt if it is just hanging out though, would definitely get shot around these parts if not in the area for a specific reason lol. That voltage was specifically found on the gray and orange wires and it was on its way to the coils.
By the way, when you were checking the fuel levels in the float bowls it seemed that per your original problem of carbon fouling the spark plugs that you never did the running fuel level test, only the bench test:
*Did you do the running fuel level test?*
Really don’t want to go back to carbs till absolutely certain the voltage readings are good. If 8.4v at idle feeding a coil is in spec then all is well and I will deal with fuel again, but when I couldn’t get a leaner condition at any of the 4 bench set levels I decided that operation is above my pay grade. When top of lip, middle of lip, bottom of lip, and 3mm below bottom of lip won’t find a sweet spot then it’s beyond me for the moment. Dang good at getting even level settings though. Hit within the width of the tension surface of the fuel 3 outta 4 times.
Someone on here posted that there should be no voltage drops in the system when the key is switched on. Sounded sort of like an ignition vs carburetion thing and had “chasing the smoke” in it a lot. Can’t find reference to what voltage specs are at the coils and hope that while they were chasing that smoke they recorded the test points and values and will share if they read this. Did I mention that there is no voltage drop if the stator is isolated from the circuit? On this bike if you unplug the 2 wire connector behind the fuse panel that goes to the alternator/stator the voltage drop goes away. Just don't be taking a shower and watering your lawn when you do it or it might not work though lol.





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[Barbarosa]

And I keep saying if the stator is isolated there is no voltage drop. Got stuck in a loop on that and keep saying stator when it is actually the field coil that is isolated. Another senior moment brought to you by brain farts.

[3Phase]

No one is being sarcastic or condescending but you do need to stop unplugging the field coil and measuring voltages, it's stressing you out.

Twice now you've measured and posted that you have 12.6V at the battery and 11.5V at the fuse box. That's a 1.1V drop where it should be no more than 0.1V. You will always have a small voltage drop across the Main fuse because it is a resistor and when it gets too hot it blows but there should be almost no voltage loss from the battery to the fuse box.

The voltages you've found are a little low but not enough to cause misfires and foul the spark plugs, especially if as you say it pulls and runs smooth at higher RPM where it needs more current to make sparks and light the fires, not less.


Start with cleaning the connections from the battery to the Main fuse, then mover to the harness connector for ignition switch, the switch itself, then the fuse connection in the fuse box.

From the fuse box, follow the Red/White wire.

Clean the harness connector for the right-hand handlebar control and the kill switch like motoman suggested and that should take care of the voltage drops

The entire Ignition circuit is run with a Red/White wire from the fuse box to the kill switch, coils, TCI and the Start solenoid so when you mention it you need to describe exactly where it is that you're talking about.

The White/Red TCI wire voltage you keep measuring is the +12V Start wire and it's tied to the splice/junction for the coil primary windings so it will always have the same voltage as the coils except when the Start button is pressed, then it will have 12V.


The delay for the headlight to turn on after the engine starts is puzzling and I'll have to think about it. Does the headlight stay on if you kill the engine with the kill switch or does it shut off immediately?

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[Barbarosa]

I have put a total of 16 miles (4 rides) on this bike, and most of that it was limping, so not much actual running data. PO said he bought a Goldwing and just quit riding this one and the bike was “running” when put up. I’m thinking now that it started having running problems, he got tired of changing plugs, and then got shop rate sticker shock and just bought another ride. The bowls were squeaky clean when I checked the fuel system before the initial start up. It kicked and snorted at first as it came back to life and actually ran close to right for a while. Then it started dropping random cylinders. Visually there was plenty of spark so next step, go through the carbs. They were not spotless so they were cleaned. There was an odd looking float valve so they were all replaced. The jets were not mikuni so they were replaced. The float levels were in question so I set them in equal ranges to cover every position on the bowl lip and even 3mm below just to see if a lean condition could be induced. Even tried closing the gap on the plugs. They still carbon foul during dial in with a dry sooty coating that can be wiped off with a paper towel. On several other repairs I have found weak spark will cause that condition, so back to the ignition to find the voltage drop.
Did all you suggested on the wiring maintenance. When going through the wiring it is very evident that it had been serviced not too long ago. The pick up coil fix is quality work and there has been no hacking on any of the wiring. Coils, leads, and plug caps all in tolerance and squeaky clean. I disassembled all the connector plugs in the ignition circuit and scrubbed them. The main switch would not go into the fork lock or park position so I thought that might have been creating a contact problem. Fixed that and cleaned the copper to shiny even though no corrosion was present. The kill switch is a new factory replacement. I systematically isolated circuits and bypassed and jumpered switches till I got to the only thing that hadn’t been isolated, the field coil. The only way I can get that missing volt back is by unplugging it. And that’s where I’m at. Will get the headlight info to you the next time I fire it up.
I am working on the premise that there is a whole volt going somewhere, and the system is simply old and tired and is keeping the juice at just enough to fire off and run till the carbon builds up and starts messing with an already weak spark. I don’t understand why or how taking the field coil out of the circuit gets that volt back, but it’s the only way I have been able to make it happen. Funny, but I think I remember ages ago taking a “lighting coil” out of a Honda system to run without a battery. Anyway, I would sure like to know if that volt is what’s keeping this thing from being able to run well enough to finish the tuning process. Changing my troubleshooting strategy to assuring there actually is enough voltage and figuring out why not instead of hoping someone has actually seen this problem before and the switch/connector cleaning fix didn’t take.
For reference, I need voltage readings from a running bike with the same system. As a starting point the assumption is no voltage drop in the running bike. Need measurements from the larger TCI connector at the ballast r/w and the coil feed w/r. First with key on, then started and running at idle, and another with increased rpms. Also need readings from the orange and gray in the same manner. Will probably be different from bike to bike, but if the bike is running well I believe it will be reliable and useful data. So why not just humor me and someone pull off the seat, get out a meter, and see just how much voltage it takes to make the system work right. If it turns out I am chasing my tail on the voltage drop thing and it is actually getting what it needs I will take the carbs down to bones and clean again, buy mikuni float valves, and do the running level test while praying I don’t burn down the house. This old fart does appreciate the help.

[3Phase]

Ignition circuit primary voltage is not the problem.

You're not 'missing' any voltage when the field coil is connected and the battery's capacity is used to run the load any more than you are 'missing' fuel in the gas tank after a 16 mile ride.


You measured 14 Volts at the fuse with the engine running.

The ballast resistor and coils added together are roughly 3 Ohms and you measured 7 Volts at the Orange and Gray wires, leaving 7 Volts and 3 Ohms for the TCI.

There is no ignition circuit voltage problem.


My XS is in pieces at the moment and the wiring harness is unwrapped and spread out over two tables and a benchtop for repairs and upgrades but I don't need to put any of it back together to tell you that with the field coil connected and the ignition switch on there should only be a 0.1V to 0.5V drop from the battery to the fuse block.

Leave the field coil connected and find the voltage drops by measuring across each component from the battery to the fuse block. Add them together and they should equal the difference between the voltage at the battery the voltage at the fuse block.

If the battery can't supply enough current to power the field coil and keep the electrical system voltage above 12V without the engine running then battery has a problem, not the field coil and definitely not the ignition circuit.


And while you troubleshoot, remember that this is supposed to be fun!

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[Barbarosa]

Thanks for the input, but not doing any more electrical testing till I find out the voltages at the TCI of a same system well running XS1100. Really want to make sure the coils are getting what they need. Hopefully someone that sees this thread will take the readings or have good resource for that information. Not planning to buy a running bike to find out, but you never know lol. When I get those values and compare them to what this one is doing I will take it from there.

[3Phase]

I don't blame you at all and I wouldn't buy another bike just to check the voltage either!

Mine's not quite typical because I can see the voltage on the analog gauge I have mounted on the handlebars. The gauge is periodically checked against my digital handheld meter so I don't ride along all fat, dumb, and happy with a bad gauge and demolish the battery. I did that once upon a time so that's why I have the gauge now and why it gets checked.


Before I tore the engine down for rebuild, the alternator was putting 14V to 14.8V into the system when running and the battery held 12V to 12.5V (AGM battery) with the key on, engine off.

The field coil was of course connected but the headlight relay was bypassed too so it came on with the key before the engine was started and together they drew 80W to 120W.

The last time I checked the voltage at the ignition coil negative side to the TCI was closer to 8V but I have run the 26A XJ1100J alternator and its matching Regulator/Rectifier instead of the stock 20A XS1100G charging system along with a set of Accel 3 Ohm coils and no ballast resistor so it's not really a 1:1 comparison to the ignition in your stock 'SG.

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