Charging system woes on GS750

[Candyman]

The bike died on me the other day and wouldn't restart. She was totally dead, wouldn't even tick when I hit the starter. Bump started it and the headlight went really bright then burnt out, tack also burnt out (smoke from gauges). Got it home and did some testing on the battery, it looks like it shorted out. But I don't think thats my only problem.

I tried a known good battery but I could barely get it to start, let alone run. When I did get it to run it it would only run on choke, would not idle, and would not rev. I put in a new headlight and it did the same thing, had light for about 30 sec then it got really bright and blew the bulb. This is suggesting to me the R/R is not doing its job anymore. As it is right now, I can only get the bike to start while on a charger, then it will die as soon as I take the charger off. Testing as per the stator papers (@ 5k rpm ect) is not possible; if I try to do ANYTHING with the throttle, it tries to die on me.

I tested resistance between all possible pairs of the stator wires with the bike off and came up with about 1.3 Ohms, which according to the stator papers is a good sign for the stator. Though I'm not sure it totally rules out stator trouble. ???

Checked and cleaned as many connections as I could get my hands on. Some were fairly corroded, and in the course of checking things over I noticed it looked as if someone had already been tampering with the mounting screws for the R/R.

I have been reading the very helpful Stator Papers as well as the electrical odds and ends on Basscliffs site, helping me learn a lot about the charging system on these old girls. But I just wanted to run a couple questions by you folks before I go making investments in parts I may not need.

First, from what I described, does it sound reasonable to suspect the R/R first?

Second, would I be safe to replace the R/R and leave the stator until I can test it with a known good R/R?

And finally, the bike is an 84 GS750E as per the ownership, but the VIN has an "83" in it. The reason I mention this is because it looks for the 80-83 GS750E they used one part #. But then in 84 they only list the GS750ES, and it takes a different R/R part #. I'm thinking my bike is actually an 83...?

Appoligize for any confusion in the description, and thanks for any help.

 

[koolaid_kid]

It most certainly sounds like the regulator is not regulating. Personally, I would replace it asap and then recheck your charging system.
Where are you located? There may be someone near you who has a spare R/R that you can use to test with.
Hint: Select the User CP (upper left menu item) and update your location. It is also helpful if you put your bike info in your signature, even if you are not completely certain of the model year.

 

[spyug]

Sorry to hear of your problem. Mine is an 83 750 and I had charging problems too ( bike had sat for 7 years before I got it). I found that the R/R didn't seem to be working but when I replaced the connector with spades and added a seperate ground lead from it directly to the battery it came to life and started charging like a banshee.

Almost 4 years on it is still working but there are some signs that its starting to fail. I run a volt meter to keep an eye on things as I ride and the odd time now I see the needle flip to the discharge side, then back to charging. Occasionally, the needle flips to the neutral mark and stays there for a few minutes. Its likely time for a new one.

So the short answer to your question could be that the R/R is suspect at this point the stator doesn't seem to be the issue. Try the ground lead mod and make sure all your connectors are indeed clean and tight.

Good luck with it.
Spyug

 

[Candyman]

I'm located just north of London Ontario.

Glad to hear I'm not the only one who suspects the R/R.

I'll have another look at the ground lead mod and maybe give it a try. Nothing to loose, and I will be doing it anyway if I get a replacement so no harm in chopping the wiring.

Still wondering about the R/R part # mystery... Anyone with guidance on that one?

Thanks for the input.

 

[Guest]

You do need to change the R/R, but certainly not a Suzuki part number. There are a lot more modern and effective R/R's out there. I doubt if you had any regulation going on at all with your smoking results. Do check all the connectors on the bike, headlight, under seat, especially stator leads, etc. replace all burnt connectors and clean and apply dielectric grease to all the connections. I had a large connector that was getting hot. Soaked the connectors in simple green over night, rinsed them in clear water used an air gun to remove the water, let them dry several hours and filled the connector with dielectric grease. Plugged them together, wiped of the excess that squeezed out, and it runs absolutely cool to this day.

 

[spyug]

Still wondering about the R/R part # mystery... Anyone with guidance on that one?

I didn't know that but i suspect it is just a superceded part...so likely identical just renumbered. In anycase, the R/R is one part that can be swapped out for any number of different models and from different makes of bikes too. There is a gigantic list of them somewhere here so do a search for replacement R/Rs. The Honda models are supposed to be better than ours and our friend Duaneage had been selling them, but sadly is no longer able to.

If you have a local bike wrecker you can wander in with yours and match it up to something similar. Our bikes have 5 wires but some like the Hondas have a sixth "sense" wire which is usually tied in to the tail light circuit to keep an eye on voltage.

There are also more modern alternatives and I believe there is a lot of info floating around so again, do some searching.

Good luck,
Spyug

 

[koolaid_kid]

Here is one replacement list: http://www.thegsresources.com/_forum/showthread.php?t=134690
BassCliff also has one on his web site; I have not compared them but either (or both) should get you on the road to recovery.
I use a Honda FET model, but posplyr has a ton of info on the CompuFire series regulator.

 

[Candyman]

Ah, I had another look at the "big list", I didn't realize stators were on there too, thats where I was getting different part numbers.

I copied the list of R/R's from Hondas that will work and I'll do some shopping tonight.

Anyone else have hopes that my stator might very well still be good in this situation; Or am I just wishful thinking?

 

[BassCliff]

Hi,

Have you had a chance to check, clean, and repair all of the electrical connections and grounds on your bike? This is a good thing to do just for general maintenance, plus it helps your charging system stay healthy. Look for discolored, melted connectors and wires under the tank, in the headlight bucket, behind the side covers, etc.

Have you done live testing on the stator? With a known good, fully charged battery, you can disconnect the r/r unit and let the bike run on battery power while you do the live tests on the stator. You should get around 70 volts AC from each pair combination. But even this test is not 100% conclusive. I've had a stator pass this test in the garage but then I get on the road and the battery wouldn't be charging. I'm pretty sure this was because some of the insulation on the windings was melting away and it would charge OK until the stator got hot and the windings started shorting out. So just keep in mind that all of the stator and r/r tests will definitely tell you if you have a bad one, but they won't absolutely prove that you have a good one.

But, yes, I would replace the cheaper r/r part first and re-test (after cleaning up the wiring harness, fuse box, ignition switch, etc.). Connect the ground wire from the r/r unit directly to the negative battery terminal or use Mr. posplayr's "common ground" technique. Good clean grounds are very important. Connect all three output wires from the stator directly to the input wires on the r/r unit. And again, check and clean ALL of the electrical connections on the entire bike. Sometimes you can't see corrosion but it will still have an effect. De-Oxit is a good spray cleaner and along with a little wire brush will take the resistance right out of all those connections.


Thank you for your indulgence,

BassCliff

 

[Candyman]

Checked and cleaned as many connections as I could get my hands on. Some were fairly corroded...

I wasn't aware I could test the stator with the r/r unplugged, I might give that a try tonight and see if it will run any better. As I said, I couldn't do any live testing on the stator because the bike would not start or run properly as it is right now. Might be a different story if I disconnect the dud r/r?? Hope so. Thanks for that info.

 

[BassCliff]

Hi,

I wasn't aware I could test the stator with the r/r unplugged...

I invite you to read the following:

The Stator Papers

More On The Stator Papers

GS Charging System Health+Quick Test

Cleaning Your Wiring Harness

Fusebox Cleanup

​

Stator Test

​

Stator Replacement

​

Regulator/Rectifier Replacement


Keep us informed.

Thank you for your indulgence,

BassCliff

​

 

[spyug]

I just reread the original post where you mention smoke coming out of the guages. That doesn't sound good and makes me think other things are happening.

I think you should have a close look at the harness up at that end and check all the connections and wires there abouts. There are several hot leads in that area including the main one into and out of the killswitch/starter button. It sounds like something has overheated and started to fry things which, if not attended to ,could cause you more issues. Check this before you try and get her running as it could be serious & costly. Do you have a wiring diagram to follow? If not pull down one from Cliff's site.

Charging issues are definitely a pain but all the info here will get you sorted.

We are pulling for you and will follow along to see how you make out.

cheers,
Spyug

 

[Candyman]

Thanks BassCliff, there was one there I hadn't read through. There is one article about the common ground mod, I remember reading it but I can't seem to find it again. Anybody know where that one is?

So much info on the site its easy to loose track of it all sometimes

 

[Candyman]

Well, replacement Honda r/r on its way to me. On hollidays next week so I won't be able to get back to it for a while. I'll post and let you know how things go then.

 

[BassCliff]

Hi,

There is one article about the common ground mod, I remember reading it but I can't seem to find it again. Anybody know where that one is?

I do believe that is the "GS Charging System Health" article from Mr. posplayr. I have a copy on my website at the link in my previous post. It's good stuff. That posplayr is much smarter than he looks.



Thank you for your indulgence,

BassCliff

 

[Candyman]

ah yes, I missed the pdf link tucked in there, thanks