81 GS550 - charging problems

[D-Mac]

Hi all,

I've been trying to diagnose a charging problem on an 81 GS550 I bought a couple of weeks ago. As the previous owner told me when I bought it, it doesn't charge (voltage on a fresh battery doesn't increase when the bike is running).

I used the diagnostic on the Stator Papers to test various components. Rectifier tested ok with all tests. All stator tests (continuity, ground, and AC check) all test OK. I even jumped each connector to verify that it wasn't at any of the connectors. I'm currently taking a mechanics course, so I'm confident I did the stator test properly (that's all they teach you).

Question.....

When I did the first tests found in the Stator Papers (checking + and - connections between the battery and rectifier), I got NEGATIVE 0.5v for both the positive and negative tests with the bike running. The Stator Papers say anything less than 0.2v is OK. I hooked everything up EXACTLY as the directions indicate. So does a NEGATIVE value here mean I'm ok? For what it's worth, I also checked the conductivity between the rectifier and battery leads and they tests OK as well.

I'm kind of at a loss at this point.

[BassCliff]

Hi,

On my bike I have had the stator pass all the tests, both passive resistance tests and active AC tests, while the bike was cold, sitting on the center stand in my garage. But after riding for a while the battery would not be charged. It seems after getting hot the stator windings would move and short because the insulation had either melted or worn off.

Are all the legs reading exactly the same resistance? If there is any variance I would be suspect. Is there any continuity to ground with any leg? Are all three legs giving you exactly the same AC output?

For reference:

Stator Test

More On The Stator Papers

GS Charging System Health+Quick Test

Regulator/Rectifier Diode Test

When testing for voltage loss between the r/r output and the positive battery terminal, you may have had your test leads reversed. Any voltage measured there is a direct result of loss due to resistance. Clean the connections in the charging system, clean the fusebox, etc. Connect the ground on the r/r unit directly to the negative terminal of the battery. Make sure all of the ground connections and battery terminals are clean.

If you are sure that your stator is OK then you have to suspect the r/r unit. But usually when the r/r fails it will start over-charging.


Thank you for your indulgence,

BassCliff

[tom203]

Hi all,

I've been trying to diagnose a charging problem on an 81 GS550 I bought a couple of weeks ago. As the previous owner told me when I bought it, it doesn't charge (voltage on a fresh battery doesn't increase when the bike is running).

Have you eliminated the useless stator loop thru headlight switch? Made sure that you have a solid ground from R/R to battery negative? As Basscliff said. both stator and R/R can test OK, but fail to deliver the ten + amps needed to run ignition and lights and have a little leftover to charge battery.

[D-Mac]

Lots to think about.

Stator legs tested out perfectly (AC voltage is within spec and the same for each pair of stator legs; each pair of legs has the proper resistance on that test; none of the legs are grounded).

I do think it's the wiring - perhaps just too much voltage drop through it. I've run a wire straight from the R/R ground to the neg. battery terminal, so that one should be covered (I will test to confirm tomorrow). I'll also look more closely at the positive connections tomorrow and eliminate the unnecessary loop.

Thanks everyone. I'll keep you posted.

[D-Mac]

OK. I eliminated the silly loop through the headlight (all there stator legs now go director to the R/R).

I re-checked the voltage drop through the positive loop (battery positive to red wire coming from the R/R) and it was -0.5v with the bike running and the revs up. ***So that means I'm losing 0.5v through the wiring harness, correct?** Not great, since my read of the stator papers indicates that this will cause me to lose 0.5v when charging the battery (there is no sense wire on the R/R to compensate for any voltage drop on this bike).

I then checked the loss through the negatives (between battery negative and ground wire from the R/R). Another -0.55v when running. Not very good either.

So I think this means that I'm losing about a volt of potential charging through the harness alone. Still, that alone doesn't seem to account for the lack of charging (although perhaps with a tired stator it might). To reduce this issue, I connected the R/R ground directly to the battery negative to eliminate the 0.5v loss through that loop. On re-checking the bike with it running, the battery voltage STILL doesn't come up at all (I started at 13.1v with the battery and bike not running, it drops a little with the ignition switch on as you'd expect, and when running and revving it up it does not move up last the low 12v range). In fact, it's exactly the same as when I started.

So I think I've learned that my harness is not very efficient (not surprising since it looks terrible), but that it would not seem to be able to explain (alone) why my charging system is toast. I suppose it could still be a bad connection somewhere, although I've jumped every one and re-tried it. My stator or R/R are likely not cutting it I think. They do pass the various tests minimally and everything else is accounted for. I will likely replace both AND re-do the harness in an attempt to get things to improve. My gut tells me it's the R/R, but I don't want to replace it only to fry another one if it's a bad stator. I did find it hard to get exact readings when testing the AC output from the stator, so I suspect I might have short within the windings (causing it to under-perform). If the stator looks anything like the other wiring on this bike, it's likely shot.

[tom203]

Personally, I'd replace the R/R no matter what, especially if it's the stock one or an aftermarket mini one.You can test the main rectifing diodes in the R/R easily, but the regulating circuit is difficult to assess, except by running bike at different rpms and for period of time to see how it does hot. Used Shindengen R/R's (common on hondas) are cheap and proven reliable-search this site.I'd redo the stator tests-especially the ohm test-, you might find an obvious fault. IMHO, a decent R/R won't destroy the stator, but a bad stator could cook a wimpy R/R.

[1_v8_merc]

I won't even waste my time testing GS charging systems anymore...
I just automatically rip out the Stator/RR and throw It in the scrap pile and order Replacements.
(of course this is only on bikes running Stock units...since those factory units were the problem)

I had the same problem as you, I was trouble-shooting my 650 for months, and I couldn't find anything majorly wrong with all the Volt Tests.
I finally ponied up the cash and bought a new Stator and RR, and FIXED!

[D-Mac]

Yup. It has to be the R/R and/or the stator.

I started tearing down the bike today. Both will be replaced as part of the project.

Now to figure out how to remove all the exhaust bolts that are snapped off...

[verde]

Do the stator check running the bike on battery power, multi-meter on VAC. Between any 2 of the 3 stator leads it should be ~15-20 VAC at idle and climb to ~60VAC at higher RPM. It should be the same between any two leads at the same RPM. If that checks out then a good reg/rec directly wired will get you sorted.



And here's a great reference on finding a quality modern reg/rec and why you want to use a regular size in-line fuse for this mod:

http://www.triumphrat.net/speed-triple-forum/104504-charging-system-diagnostics-rectifier-regulator-upgrade.html

[D-Mac]

Do the stator check running the bike on battery power, multi-meter on VAC. Between any 2 of the 3 stator leads it should be ~15-20 VAC at idle and climb to ~60VAC at higher RPM. It should be the same between any two leads at the same RPM. If that checks out then a good reg/rec directly wired will get you sorted.



And here's a great reference on finding a quality modern reg/rec and why you want to use a regular size in-line fuse for this mod:
http://www.triumphrat.net/speed-trip...r-upgrade.html

Thanks! Nice diagram. Stator AC output was a bit funky when I tested it the first time (when I revved it up one set of legs jumped you to over 80v before settling down at ~55; other pairs moved up more smoothly to ~60v when tested).

When I connected the R/R directly between the stator and the battery, the battery still wouldn't charge.

So the R/R is toast. Stator is suspect and will probably be replaced depending on how things look. I just noticed a super-nice '81 GS550T a few hours away for cheap. It would make a good parts bike (or more like my current GS would make a good parts bike for it!) so if I buy it as part of my project, I'll probably swap out the R/R. Otherwise, I'll just find a replacement at some point.