Need Charging System Help

[gbw]

77 GS750B. Need help figuring out what is going on with the charging system.

The last time I did this a few years ago I went through everything and could never get it charging right. I bought a few newer bikes and have been riding them for the last couple of years. Now I need the GS to be my primary ride for a couple of seasons so I really need to get this figured out.

* Stock R/R checks out ok but I replaced it with a duaneage R/R.
>R/R wired directly to battery + and -.
* Stock stator checks out but I replaced it with another stock one Wazz gave me.
* Battery tested ok but I replaced it with a fairly expensive gel battery.
* I've been through the wiring harness and cleaned and/or replaced every connection I can find. Replaced the glass fuse with an automotive type fuse. Have a good ground connection between the battery, frame, and engine case.
* I also did the coil relay mod. Not sure I need to, but I did anyway.

Bottom line, at 5k rpm I never get above 12.8VDC.

Everything checks out according to the Stator Papers. So, my question:
If the R/R, stator, and battery are good, what else would keep me from charging properly?

Data from Stator Papers:
Phase A Tests:
* Voltage at 2500 rpm: 12.6V
* Voltage at 5000 rpm: 12.8V
* Voltage drop from R/R output to battery + terminal: 0.05V
> When not connected to the battery the R/R puts out plenty of voltage. Up to and above 50VDC when I rev the engine
* Voltage drop from R/R ground to battery neg terminal: 0.18V
> I measured this form the R/R case to the battery neg terminal. My R/R neg wire is connected to the battery's neg terminal.

Phase B Tests:
* Resistance between each stator wire: 1.1 Ohms consistent across all three wires
* Resistance between each stator wire and chassis ground/engine case: infinite. consistent across all three wires
* AC voltage from stator at 5k rpm: 80VAC. Consistent across all three wires.

Phase C Test:
* The R/R passes all the diode tests. I believe the R/R is good.

Of course the Stator Papers say if you perform all these tests and the stator and R/R are ok, then you have a bad battery. However, my battery is known good.

I'm trying to think if I left anything out. This post is already too long but I wanted to include as much info as I could.

Finally, I tested the current draw without the bike running:
Ignition off: 0A
Ignition on, headlight off: 5A
Ignition on, headlight on low-beam: 8A
Ignition on, headlight on High-beam: 10A
*I think these are all about right, but figured I'd throw those in the mix as well.

[posplayr]

77 GS750B. Need help figuring out what is going on with the charging system.

The last time I did this a few years ago I went through everything and could never get it charging right. I bought a few newer bikes and have been riding them for the last couple of years. Now I need the GS to be my primary ride for a couple of seasons so I really need to get this figured out.

* Stock R/R checks out ok but I replaced it with a duaneage R/R.
>R/R wired directly to battery + and -. (Where is the Sense wire connected?)
* Stock stator checks out but I replaced it with another stock one Wazz gave me.
* Battery tested ok but I replaced it with a fairly expensive gel battery.
* I've been through the wiring harness and cleaned and/or replaced every connection I can find. Replaced the glass fuse with an automotive type fuse. Have a good ground connection between the battery, frame, and engine case.
* I also did the coil relay mod. Not sure I need to, but I did anyway.

Bottom line, at 5k rpm I never get above 12.8VDC.

Everything checks out according to the Stator Papers. So, my question:
If the R/R, stator, and battery are good, what else would keep me from charging properly?

Data from Stator Papers:
Phase A Tests:
* Voltage at 2500 rpm: 12.6V
* Voltage at 5000 rpm: 12.8V (It seems to be charging some 12.8v is more than 12.6v at 2500 RPM)
* Voltage drop from R/R output to battery + terminal: 0.05V (Did you measure this at 5K RPM (i.e. full electrical load)?
> When not connected to the battery the R/R puts out plenty of voltage. Up to and above 50VDC when I rev the engine (You dont want to disconnect the R/R red wire from the battery and run the bike)
* Voltage drop from R/R ground to battery neg terminal: 0.18V(Did you measure this at 5K RPM (i.e. full electrical load)? It is very high and way too high if you did it at idle
> I measured this form the R/R case to the battery neg terminal. My R/R neg wire is connected to the battery's neg terminal.

Phase B Tests:
* Resistance between each stator wire: 1.1 Ohms consistent across all three wires
* Resistance between each stator wire and chassis ground/engine case: infinite. consistent across all three wires
* AC voltage from stator at 5k rpm: 80VAC. Consistent across all three wires.

Phase C Test:
* The R/R passes all the diode tests. I believe the R/R is good.

Of course the Stator Papers say if you perform all these tests and the stator and R/R are ok, then you have a bad battery. However, my battery is known good.

I'm trying to think if I left anything out. This post is already too long but I wanted to include as much info as I could.

Finally, I tested the current draw without the bike running:
Ignition off: 0A
Ignition on, headlight off: 5A
Ignition on, headlight on low-beam: 8A
Ignition on, headlight on High-beam: 10A
*I think these are all about right, but figured I'd throw those in the mix as well.
Seems you are beyond this now but did did you do a Quick Test?

The modified stator pages that I put together clairify that the voltage drop tests need to be done at full load (i.e. 5K RPM) otherwise they are meaningless.

I suspect you have a poor connection somewhere between the R/R(-) and your battery. That is why you are seeing 0.18V .

[mike_of_bbg]

I like the idea of running a second direct wire from the battery ground, and the R/R ground, to one of the R/R mounting bolts.

[gbw]

Thanks for reading my post and for your questions!

Where is the Sense wire connected?

To the rear brake switch. To the side of the switch that has battery voltage when the ignition switch is on.

Voltage at 5000 rpm: 12.8V (It seems to be charging some 12.8v is more than 12.6v at 2500 RPM)

Yeah. Just something is keeping it from getting to where it needs to be.

Voltage drop from R/R output to battery + terminal: 0.05V (Did you measure this at 5K RPM (i.e. full electrical load)?

No. This was measured at idle. I'll retest at 5k. I have a connector on the R/R lead that goes to the battery and I measured at this point. Of course since I have the R/R connected to the pos battery terminal, there is no loss at that point (at the pos battery terminal).

When not connected to the battery the R/R puts out plenty of voltage. Up to and above 50VDC when I rev the engine (You dont want to disconnect the R/R red wire from the battery and run the bike)

whoops. I won't do that again.

Voltage drop from R/R ground to battery neg terminal: 0.18V(Did you measure this at 5K RPM (i.e. full electrical load)? It is very high and way too high if you did it at idle

No, measured at idle. I'll retest at 5k rpm and report back. Also, where should I measure this from? The neg wire from the R/R is connected to the battery neg. Obviously I can't take both measurements at the battery's neg terminal. I took the measurement's from the R/R's case to the neg battery terminal.

Seems you are beyond this now but did did you do a Quick Test?

I walked through it quickly and seemed to be pretty good but didn't record the results. I'll go through it and report back.

The modified stator pages that I put together clairify that the voltage drop tests need to be done at full load (i.e. 5K RPM) otherwise they are meaningless.

I suspect you have a poor connection somewhere between the R/R(-) and your battery. That is why you are seeing 0.18V .

I'll pay close attention to the neg side of the R/R, but figured I was ok since I have the R/R's neg connected to the battery's neg. But shouldn't that also correspond electrically to the R/R's case?

My plan is to go through the wiring harness again looking for anything out of sorts. Also, I'll pull the oil pressure switch and the turn signal relay and test for charging voltage again. These are really the only loads other than the coils.

I won't get to work on the bike again until mid next week so I'll report back once I can get back out in the garage.

Thanks again,
Greg

[posplayr]

Thanks for reading my post and for your questions!


To the rear brake switch. To the side of the switch that has battery voltage when the ignition switch is on.

Yeah. Just something is keeping it from getting to where it needs to be.


No. This was measured at idle. I'll retest at 5k. I have a connector on the R/R lead that goes to the battery and I measured at this point. Of course since I have the R/R connected to the pos battery terminal, there is no loss at that point (at the pos battery terminal).


whoops. I won't do that again.


No, measured at idle. I'll retest at 5k rpm and report back. Also, where should I measure this from? The neg wire from the R/R is connected to the battery neg. Obviously I can't take both measurements at the battery's neg terminal. I took the measurement's from the R/R's case to the neg battery terminal.

If you have a straight wire from the R/R(-) to the Battery (-) and there are no connections or solder joints in between then there is nothing to measure. Don't measure from Battery to R/R case that is probably not reelvant. But it begs the question how did you extend the R/R(-) wire to get from the R/R to the battery?

I walked through it quickly and seemed to be pretty good but didn't record the results. I'll go through it and report back.


I'll pay close attention to the neg side of the R/R, but figured I was ok since I have the R/R's neg connected to the battery's neg. But shouldn't that also correspond electrically to the R/R's case?

The case may not be the same as R/R(-), according to Duanage it normally is not. My SERIES R/R it is one and the same.
To truth it s sounding like the R/R is over regulating.

My plan is to go through the wiring harness again looking for anything out of sorts. Also, I'll pull the oil pressure switch and the turn signal relay and test for charging voltage again. These are really the only loads other than the coils.

I won't get to work on the bike again until mid next week so I'll report back once I can get back out in the garage.

Thanks again,
Greg

Your problem seem like it maybe possible that the stator is going out even though it tests correctly with an ohm meter. There is a thread here where I was exploring alternatives to the current stator tests both in the manual and in the stator pages because they can be inconclusive. Some people have chased their tails for a couple of weeks while a marginal stator was intermittently failing with temperature depended behavior.

Graham has a test that he performs which is apparently very reliable; in addition to checking AC voltage between each leg (the 80VAC result you got at 5K RPM) he checks also checks for the absence of AC voltage between each leg of the stator and ground. There should be no voltage unless there is a short.

The only problem with that test is that it is still an unloaded test. I had investigated doing a loaded test with a dummy load. However it just occurred to me that there is no reason that you cant do Grahams test while the R/R is still connected and under load at 5KPRM. There should still be no AC voltage.

So theoretically the best and easiest loaded test is as follows:

1.) Keep the R/R connected to battery and the stator
2.) Put the Volt meter on the AC setting


3.) With the engine at 5K RPM: alternately check for any AC voltage between each stator leg and ground.

• Leg 1 and engine case SHOULD be ZERO ( e.g. less than 1 VAC)
• Leg 2 and engine case SHOULD be ZERO ( e.g. less than 1 VAC)
• Leg 3 and engine case SHOULD be ZERO ( e.g. less than 1 VAC)

If you fail any of these then your stator is shorting and bad. This should be a very good test as it is actually a loaded test.

http://www.thegsresources.com/_forum/showthread.php?t=174130

[Redman]

77 GS750B. Need help figuring out what is going on with the charging system.

The last time I did this a few years ago I went through everything and could never get it charging right. I bought a few newer bikes and have been riding them for the last couple of years. Now I need the GS to be my primary ride for a couple of seasons so I really need to get this figured out.

* Stock R/R checks out ok but I replaced it with a duaneage R/R.
>R/R wired directly to battery + and -.
* Stock stator checks out but I replaced it with another stock one Wazz gave me.
* Battery tested ok but I replaced it with a fairly expensive gel battery.
* I've been through the wiring harness and cleaned and/or replaced every connection I can find. Replaced the glass fuse with an automotive type fuse. Have a good ground connection between the battery, frame, and engine case.
* I also did the coil relay mod. Not sure I need to, but I did anyway.

Bottom line, at 5k rpm I never get above 12.8VDC.

Everything checks out according to the Stator Papers. So, my question:
If the R/R, stator, and battery are good, what else would keep me from charging properly?.....
......
......
......

Hi Greg.

Hum. You seem to have checked things out quite well and have made a concise report.

Hum, 12.8, and no voltage drop from R/R to battery on positive and on negitive*.

As something of a test of the stator and R/R ; lift the scence wire, that will make the R/R think the voltage is real low and then the R/R will put out its maximum capacity.

Hum, you say R/R is connectred directly to the battery. Directly, as in no connectors, ther R/R wires were lng enough to reach the battery + and -.
Or do you mean, say, the solenoid post for the battery + and some ground point for battery - .... ?

* when you said you measured from R/R ground to battery negitive, do you mean the R/R case? or the R/R ground wire?

>>>>later note:
This bike I suspect

[gearhead13]

Resistance between stator legs has always been .6 ohms for me, 1.1 seems kinda high
My + and - wires from my R&R go directly to the battery. Ground from the bat to engine and to frame.
I also had problems with my charging system, I decided to get rid of all the spades and soldered everything and its great ever since. All my spade connections were warm/hot to the touch at idle.
My sense wire goes directly to the switched 12v source at my coil relay. That ensures it sees proper bat voltage.

[duaneage]

I have found that stators which truly measure more than 0.8 ohms per leg are toast. They might still generate 60 volts into a voltmeter, but can't take the 10 amps load of the bike.

I don't see a problem with running the bike without a battery. You'll get a rough DC voltage for sure, but the bike should be able to run without a battery, or the stator/RR is not able to do it's job. For a short test it's OK to do that.

[Redman]

Greg,

I have not had the expereince one way or the other, but theroretically I can see it is entirely possible that a stator can put out the 60-70-80 volts in the test (which is open circuit, no load, no current) but then when connected back in the circuit (under load, with some current) fall on its face, especailly after it heats up.

Dave

.

[tom203]

Greg,

I have not had the expereince one way or the other, but theroretically I can see it is entirely possible that a stator can put out the 60-70-80 volts in the test (which is open circuit, no load, no current) but then when connected back in the circuit (under load, with some current) fall on its face, especailly after it heats up.

Dave

.

I agree, so after all the tests, the best test is in the bike, ride it and see how it performs under load and in 250 degree crankcase heat. Rig up a temporary meter to monitor voltage output- couple hours of riding should be conclusive.

[gbw]

So something someone said earlier in the thread got me thinking.

So, I went out and put the V meter across the battery before I started the bike. The bike was stone cold.

While cold the bike charges just fine. 13.5VDC at 2500 and 14.7VDC at 5000 RPM. I didn't have time to let it really warm up and keep testing, but I know that my previous test were preformed while the bike was at normal operating temp.

So, what would change as the bike warms up? I'm thinking the stator is the most likely suspect.

Joe Nardy is going to loan me a know good stator (the one that got the Cedar Rapids boys home to IA from WI a year or two ago) and I'll see if that makes any difference.

[tom203]

Those are good readings- before I went playing with stator, I'd doublecheck my readings when warm . your sense wire to brake light switch should give a 14.5 v or more reading at battery- I run my sense wire direct to battery and get "only" about 14.3 fairly consistent above 2k rpm.

[TheCafeKid]

So something someone said earlier in the thread got me thinking.

So, I went out and put the V meter across the battery before I started the bike. The bike was stone cold.

While cold the bike charges just fine. 13.5VDC at 2500 and 14.7VDC at 5000 RPM. I didn't have time to let it really warm up and keep testing, but I know that my previous test were preformed while the bike was at normal operating temp.

So, what would change as the bike warms up? I'm thinking the stator is the most likely suspect.

Joe Nardy is going to loan me a know good stator (the one that got the Cedar Rapids boys home to IA from WI a year or two ago) and I'll see if that makes any difference.

Greg:
If you didn't know already, you cannot use a common GS stator in your 750. Early 77-79 750 models had a 12 pole stator. I'm not sure when, probably 1980 when they eliminated kickers on all large models, they went to an 18 pole stator. This requires a different rotor. I am not positive, as I've never measured output, but with an 18pole stator and a rotor designed for a 12 pole stator I am not sure it would adequately charge. Someone here with better experience in that department could probably fill in the missing bits I'm sure I've left out.

So the problem this causes is NO ONE currently offers a 12 pole replacement that I've been able to find. If your stator is toast, you'll either need to find a used 12 pole and hope its good, or replace your rotor with a later model 850 rotor and purchase an 18pole replacement stator.

[gbw]

Greg:
So the problem this causes is NO ONE currently offers a 12 pole replacement that I've been able to find. If your stator is toast, you'll either need to find a used 12 pole and hope its good, or replace your rotor with a later model 850 rotor and purchase an 18pole replacement stator.

Well crap. That sucks. So Joe's stator won't work for me. I should have known that.

What about this as an option: RM Stator (BassCliff sourced a replacement stator from them for his 850) has a stator diagnostic/repair service.

http://www.rmstator.com/

I completed their online form to see what they charge for this service.

Also, is the stator the same between the 750s and the 1000s? Salty Monk might have a loaner I could use for troubleshooting purposes from his skunk.

Thanks for the heads up and info Josh!

[Redman]

Interesting that charging does charge when engine cold. Wonder when it starts to degrade.
Electronics (such as R/R) problems can be temperature dependant. And so can problems with electromagnetic devices (windings, stator). so I would not know which to suspect. Maybe run it more and see when the charging system starts to degrade, and see if the R/R getting warm. Stator will be warm as engine heats up.

Ew, did not think to mention that 78-79 stator diferent than 80 and after. Josh to the rescue, again.


And, yah, the catalogs I looked at would list 80-83 or 80-85 but not 78-79.

Then I looked at ElectroSport:



Stator 12-pole Suzuki GS400 / GS550 / GS750 / GS850 (76-ON)

Part #: ESG015
Replaces OEM #:
31401-45030
31401-45011

View Product Details

$119.00