Charging system problems

[GS750GUY]

I went for a ride last night and started out with a freshly charged battery. After a couple of hours I decided to stop for a while and when ready to go again I discovered the bike would not start. Fortunately the kick start got it going again. As I approaced home, I noticed that my turn signals would come on but would only blink ocassionally and after stopping in the driveway I decided to turn it off and try restarting it. The bike would not even turn over.
To begin troubleshooting the problem, do I need to first kick start it and check the incoming voltaqe at the battery terminals to be sure it is charging at above 12 volts at idle?
Am I correct to think that if it is getting above 12 volts that the problem would then be the battery? And if below 12 volts.......then what do I look for?
Thanks,
Gs750guy

 

[spyug]

The bane of the UJM.....bad charging systems.

Before you do anything else, read the Stator Papers. Next run an extra ground from your reg/rectifier (black/white) wire dirctly to the negative post of the battery.

Fully charge your battery on a trickle charge. It should show 12.5 volts or better at rest.

Start the bike and warm up to idle. If it is ahot day or you are in a garage get a fan and point it to the motor to keep it cool.

With the bike at idle check the voltage across the posts. It should show the static voltage or slightly higher. Have your third hand or assistant roll on the throttle to about 3000 rpm and you should see 14+ volts for a healthy charging system. Anything under or over 15v and something is suspect.

If you see good charging voltage take the bike out again and try and repeat your earlier experience. If it happens again you do have a battery issue.

if you can't get good charging voltage you will need to get into the tests in the Stator papers.....but hopefully the ground lead will sort you out as it did for me.

Let us know what you find.

Good luck,
cheers,
Spyug.

 

[onchiman]

You're on the right track. The "Stator Papers" will be quite helpful. Here's the troubleshooting chart.
http://www.thegsresources.com/garage/gs_statorfault.htm

 

[jbs80106]

Autozone....

Autozone....

to further eliminate the battery, you can always take it to Autozone and they can test it for shorts and all sorts of cool things I can't think of right now....

(best bet, failed Reg/Rect.....)

 

[lurch12_2000]

If it's a failed regulator/rectifier then I would check out fellow forum user DUANEAGE for a sturdier Honda replacement for around $40. I've used his replacement one on my GS1100G for a year now with no more charging problems and just received another r/r from him to replace on my new GS1100ES purchase. What's nice is he sends you everything you need (connectors, mounting bolts,...) and is very helpful if you have questions on hooking it up.

 

[flyingace]

You first need to verify battery will hold a charge. Put it on a trickle charger or a 2 amp charger (less time of course). You should be able to obtain and HOLD at least 12.72volts. If you can't, buy a new battery.

You don't really need to be fancy about charging system testing. I shine my headlight on the wall and rev the engine. The light should brighten slightly when you do this. If it doesn't, you probably have a dead stator or R/R. I check my charging status every time I leave the garage. Of course, it's possible the charging is marginal, but this occurs a lot less than just plain zero.

 

[GS750GUY]

Thanks guys for all the advice! I've gone in and read the Stator Papers and related material and have some questions.
To boil down what I've read. Am I to understand that the GS bikes were designed for the Japanese who typically do not ride with their headlights on all the time like us Americans. And because of this am I to understand that if I ride all the time with my headlights turned on that the charging system will not be able to keep up with the demands on the battery thus I will experience instead of a battery that is being charged by the system I will experience a battery that is instead being drained by the system. Is this correct??? Am I to understand that this will happen as long as I am running with the lights on even with a perfectly healthy battery and healthy charging system? This is kind of what I'm gathering from the articles. A GS ELECTRICAL SYSTEM DESIGNED TO ONLY FUNCTION PROPERLY IF THE LIGHTS ARE USED ONLY PART OF THE TIME???????
Please let me know if I'm not thinking correctly here!!!!!
Thanks,
GS750Guy

 

[SqDancerLynn1]

Not true, it will do fine Just go thru the stator pages & you will get the problem fixed. Make sure to clean all of the stator & battery connections first, before doing the tests.. One leg of the statro runs thru the light switch, general consensus is to run the 3rd leg of the stator direct bypassing the switch

 

[GS750GUY]

Not true, it will do fine Just go thru the stator pages & you will get the problem fixed. Make sure to clean all of the stator & battery connections first, before doing the tests.. One leg of the statro runs thru the light switch, general consensus is to run the 3rd leg of the stator direct bypassing the switch

In the Stator pages it reads "The best solution is to run the (-) wire from the RR directly to the (-) terminal on the battery. Is this what you mean by the 3rd leg above?

GS750guy

 

[J_C]

NOOOOOOOOOO.

Lynn is referring to the three legs of the stator (the three wires coming from the stator. One of them goes from the stator to the harness and then to the front of the bike and turns around and comes back and yadda yadda so people just bypass that. You can see it in a wiring diagram.

The red text is referring to the rectifier/regulator ground. Stock it grounded to a bolt on the battery box. You'd be better served by running a wire from the bolt on the r/r to the battery negative terminal, instead of or in addition to the battery box

 

[BassCliff]

Cooking With Electrons

Cooking With Electrons

Hi Mr. GS750GUY,

In addition to The Stator Papers, have a gander on my little BikeCliff website at the pages Stator Test, Stator Replacement, and Regulator/Rectifier Replacement. You'll see where I've cut back and tapped off the wires running to the non-existent headlight switch and connected the three yellow output wires from the stator directly to the three input wires of the r/r. I hope it helps. Best practice is to also run the ground wire from the r/r directly to the negative terminal of the battery. Don't forget to clean all the connections, even the ground connection from the negative battery terminal to the back of the engine. I scrubbed mine with a small wire brush even if they looked clean. It made a big difference.

Thank you for your indulgence,

BassCliff

 

[GS750GUY]

Hi Mr. GS750GUY,

In addition to The Stator Papers, have a gander on my little BikeCliff website at the pages Stator Test, Stator Replacement, and Regulator/Rectifier Replacement. You'll see where I've cut back and tapped off the wires running to the non-existent headlight switch and connected the three yellow output wires from the stator directly to the three input wires of the r/r. I hope it helps. Best practice is to also run the ground wire from the r/r directly to the negative terminal of the battery. Don't forget to clean all the connections, even the ground connection from the negative battery terminal to the back of the engine. I scrubbed mine with a small wire brush even if they looked clean. It made a big difference.

Thank you for your indulgence,

BassCliff

Thanks BassCliff!! This is a tremendous help.
Due to the terrible inadequacy of my Hanes manual I need help identifying parts. On my 78 GS750EC there are two finned items that look very similar and both are attached to the battery box. Is the finned item that is attached to the bottom of the battery box the heat sink? And is the R/R unit the finned item under the left side cover bolted to the side of the battery box? If the later is the R/R unit it appears there is a single bolt through the center of the unit which attaches it to the battery box with a black & white wire also attached to this bolt. Is this the ground wire mentioned above that I have highlighted in red? If so, in addition to the wire that is already there under this bolt could'nt I add an additional length of wire under this bolt and run it to the (-) terminal on my battery?
Thanks again for your patience and help with my stupidity. Since this is electrical I want to be very careful that I don't screw this up. Also, BassCliff, what weight of wire should I use? The same that is already on this bolt?
GS750Guy.

 

[GS750GUY]

to further eliminate the battery, you can always take it to Autozone and they can test it for shorts and all sorts of cool things I can't think of right now....

(best bet, failed Reg/Rect.....)

Thanks for the tips. Good news so far. I took the battery to Autozone and the test indicated the battery is no good. Which is strange for a battery that is only a year old. I may have ruined the battery myself by over charging it. I forgot it and left it on 2 amp trickle charge overnight and noticed the battery was very warm the next morning and the charger needle indicated it was still taking 2 or 3 amps.
So on to a new battery and the system checks!
Gs750GUY

 

[BassCliff]

Cooking with electrons.

Cooking with electrons.

Hi Mr. GS750GUY,

In reading your description of your "finned parts", you may have a separate rectifier and regulator. What does your manual say? Perhaps another owner of your year and model will verify. Even so, you should be able to dump the separate units and install an integrated r/r unit. Again, hopefully a 750 owner will help us get your electrical in order.

As for wire size, the same would be OK. Going one size larger would be OK too. The more current you suspect the wire to carry, the larger it should be.

Thank you for your indulgence,

BassCliff

 

[spyug]

Glad to hear you got it figured out. I wouldn't beat yourself up about over charging it as that is unlikely. Many times I've left the trickle charger on for a day or two even and haven't managed to kill one yet. Many of the chargers will shut off when they sense a completed charge anyway. You likely just had a substandard battery.

Now to make sure things are good run that extra ground lead from the Rectifier to the battery negative pole. Fire up the bike to idle and check across the poles with your multimeter. You want to see 14V or better but not more than 15v.

I'm paranoid about having a bike that won't charge so I always put a voltage meter on any new bike I get. Chap automotive ones are usually available at the local auto store for less than $20. Cheap insurance I figure.

Now get that battery in and get out for a scoot. Summers passing8-[

Cheers,
Spyug.

 

[tomm]

Due to the terrible inadequacy of my Hanes manual I need help identifying parts. On my 78 GS750EC there are two finned items that look very similar and both are attached to the battery box. Is the finned item that is attached to the bottom of the battery box the heat sink? And is the R/R unit the finned item under the left side cover bolted to the side of the battery box? If the later is the R/R unit it appears there is a single bolt through the center of the unit which attaches it to the battery box with a black & white wire also attached to this bolt. Is this the ground wire mentioned above that I have highlighted in red? If so, in addition to the wire that is already there under this bolt could'nt I add an additional length of wire under this bolt and run it to the (-) terminal on my battery?

On your model, the part under the left side cover with the bolt through it attaching it to the battery box is the Rectifier. The part under the battery box is the Regulator.
As BassCliff suggested, you will be better off getting a replacement unit that integrates both the Rectifier and the Regulator into a single assembly.
It is a much more robust design. (Contact Duanage.)
If you stick with the current components, the problem is the regulator. It has a single lead which connects to one of the stator outputs. The ground is through the battery box, which is very unreliable. So just running a ground from that bolt through the rectifier to the battery negative takes care of your rectifier ground, but not necessarily your regulator ground. Any there is no ground wire coming off the regulator that you can run directly to battery negative.
If the regulator ground fails, then there is no place to sink any excess stator output. Result is a boiling battery and a failed stator.
The integrated replacement unit regulates the total rectifier output. There is one ground which you can run directly to battery negative. In the old design, one stator output is regulated, one is unregulated and the third is unregulated but only active when the headlight is on.

 

[GS750GUY]

On your model, the part under the left side cover with the bolt through it attaching it to the battery box is the Rectifier. The part under the battery box is the Regulator.
As BassCliff suggested, you will be better off getting a replacement unit that integrates both the Rectifier and the Regulator into a single assembly.
It is a much more robust design. (Contact Duanage.)
If you stick with the current components, the problem is the regulator. It has a single lead which connects to one of the stator outputs. The ground is through the battery box, which is very unreliable. So just running a ground from that bolt through the rectifier to the battery negative takes care of your rectifier ground, but not necessarily your regulator ground. Any there is no ground wire coming off the regulator that you can run directly to battery negative.
If the regulator ground fails, then there is no place to sink any excess stator output. Result is a boiling battery and a failed stator.
The integrated replacement unit regulates the total rectifier output. There is one ground which you can run directly to battery negative. In the old design, one stator output is regulated, one is unregulated and the third is unregulated but only active when the headlight is on.

Thanks for the terrific information regarding my bike. Problem is I have not been able to find an original manual for my bike so with the exception of what I can gleen from the Hanes manual I'm kind of in the dark on a lot of things.
I wonder if Suzuki felt at the time that a seperate regulator and rectifier would be an improvement in some ways. Here is a thought regarding the regulator........I wonder if the two bolts connecting the regulator to the bottom of the battery box is considered the ground?? Would it work to connect a wire to one of the regulator mounting bolts and run it to the negative terminal on the battery?

Thanks again!
GS750GUY

 

[spyug]

Individual regulators and rectifiers were fitted to most bikes prior to the late 70s and early 80's. Common to most all Japanese bikes. Earlier model regulators were mechanical in nature ( a set of switching points) and not as reliable as the solid state devices of today. You can still get seperate regulators and rectifiers and one company I know of http://www.oregonmotorcycleparts.com/index.html makes several types. I'm not sure if suzuki models are covered but have a look or e-mail Tony. I just got a regulator for my XS650 to replace the mechanical one and it works perfectly.

Today the combo R/Rs are fitted to bikes and the favourite conversion already mentioned is the R/R from a later Honda and Duanage is the go to guy.

In most applications, I believe, the regulator is ungrounded so fitting a lead would have no practical value. The ground lead we all mention is from the rectifier (black/white) ground directly to the negative post of the battery.

Hope this helps.

Good luck and keep us informed.

Cheers,
Spyug.

 

[tomm]

In most applications, I believe, the regulator is ungrounded so fitting a lead would have no practical value. The ground lead we all mention is from the rectifier (black/white) ground directly to the negative post of the battery.

Although I've never opened one up, I would be very surprised if the regulator on the 78 750 is mechanical and even if it was, it would still need a ground connection, there being only a single wire between it and the rectifier. In any case, the wiring diagram shows an SCR-type circuit along with a ground connection which can only be through the case.

A ground wire directly from the regulator to the battery along with a ground wire from the rectifier to the battery should help as long as the components themselves are good and all the connections are clean. But if the connections have been poor for some time, damage may have already been done and the last thing you want is for something to fail completely out on the road someplace. You're hearing a general consensus to replace it with the integrated unit. Not that expensive and a much more robust design.

 

[tomm]

Problem is I have not been able to find an original manual for my bike so with the exception of what I can gleen from the Hanes manual I'm kind of in the dark on a lot of things.

The Clymer manual, while not great, is definitely better than the Haynes manual. Also, I copied my original owner's manual for the 78 750 in pdf format and it is available on BassCliff's website.