little help with stator paper results

[brand new bike zealot]

I have a 78 550 that has something wrong with the charge circuit. At the battery, the volts read around 12.9 at idle, and drop to about 12.6 up to 5k.

Here's what I've tested...

At 5000 rpm, the vac between any pair of stator wires read somewhere around 65-70v, all about the same. A little south of the 75vac goal. Is this a major problem? I can rev it up higher to get 75vac....

The resistance between any pair of the stator wires is 1.2 ohms across the board. Within the acceptable range.

With the r/r, an aftermarket electrex about 1 year old. (The bike came to me with the separate rectifier regulator deal and a very fried regualtor) Testing across the positive of the battery and r/r, the volts are right at .2v, bouncing above and below. This is at idle of about 1300.

Testing across the negative and the ground of the rectifier it is .01 volts. Well below the limit.

I have checked and wd40'ed all connections I can find. I didn't check the r/r, as it is new, and the bike has been performing about the same since I replaced it. If the weak link is the positive charge lead, how do I replace/repair that?

Thanks for any help in advance.

[earlfor]

The spec is 80v AC output @ 5K rpm between each pair of stator legs.
If you have 65V, on all pairs, that is sufficient. The stator is working.

Usually, the problem starts with the battery. A sub spec battery that will not hold full voltage is similiar to having the charging system working to try to push energy into a short. Basically, thats what a sub par battery is. The first thing I would do is take the battery out of the bike, charge it fully and leave it sit on the bench for 24 hours. Measure the fully charged voltage and recheck it after 24 hours. fully charged should be at least 12.9 and preferably about 13V. After sitting for 24 hours, if it shows less than 12.7, its definitely ready for the trash can. I usually trash can one if it shows less that 12.8v.
Once you have a good and fully charged battery in the bike, the only thing left in the charging system is the R/R and the connections. There is a large ground wire between the battery neg terminal and the top of the transmission (under the carbs). Remove that wire, check and clean both ends and check the wire for suppleness. If you find any hard spots that will not bend, its a good bet there is internal corrosion. If corrosion, replace the ground wire. You dont say how you have the R/R connected, or what type of connectors you have connecting the R/R to the stator (three yellow wires). Ditch the bullet connectors and either solder the connections or use blade connectors. Also, check those wires for suppleness. If any have overheated and the insulation is questionable, you will need to splice in new wires. Overheating makes the wires brittle. Run an extra ground wire from the R/R case to the bike frame. Clean the contact points down to bare metal for attaching the ground wire. Run the black (DC output negative) wire from the R/R directly to the battery neg terminal. Run the R/R red wire (DC 12v output pos) directly to the battery positive terminal. Start the bike, turn the headlight on high beam and check voltage at the battery terminals at 5K rpm. It should be between 13.2 and 14.8 depending on the charge level in the battery. If it is not, since the stator is good, the battery is now a good one and the connections are direct and new, the problem can only be the R/R.

Earl

[posplayr]

I'm a newbe at GS but know more about Electrics

I have only worked on my 1981 GS750, but what I describe below probably applies to any moto charging system using 3 phase and a shunt regulator.

As you suspect the +0.2V on the positive leads is high. If you rever er up it probably goes to about +0.6V (at least mine would ; 1981 GS750). I'm not sure what finally got my "changing house in order" but here are some other ideas:

1.) I also found a final bullet connection between the RR +Pos (Red) and the + battery. It doesn't do any good to just clean them as there can be corrosion in the crimps. I crimped and soldered spade connectors to replace all bullets. On my bike all of the stator leads and R&R bullet connections to the R&R had gotten hot and in some cases melted away some of the insulation. Bullets BAD!!! :shock:

2.) I did a direct ground between the R&R case with the ground lead from the R&R. I even made a heat sink out of 1" copper tubing that seconds as a very good ground to the frame. You probably need a better R&R path to ground than the low impedance to the positive side of the battery. On my bike the is a ground tied to the battery box rubber mount and to the left side plate to make sure it is grounded. It goes into the harness and apparently establish a ground to something. There two wires were completely smoked!!! It had done some damage to the wires in the harness but not burned any. Even where the two ring lug wires were joined into the harness it did not fry (amazingly). That tells me there was a lot of current trying to get from the R&R side plate to the Frame. It probably went through the negative ground on the transmssion to get back to the battery. Moral of the story you need a beefy wire from the R&R to the negative side of the battery and I seemed to get strange results unless I grounded the R&R heatsink as well.:?

3.) For good measure I also removed the fuze box and opened it up. I used Jasco metal etch with a brush to clean it and washed with water and then careful soldered the crimp connection in there.

I think I get less that 0.1V even reving to 5000 RPM on both positive and negative leads. I did this last week (day before Xmas) so it is fresh in the memory. \\/

It would appear that all of the current that the R&R is shunting to ground needs a "VERY" good Ground (large capacity and low resistance). That is why I did item #2 above. If there is resistance the R&R low side will move above ground. Similarly current from the output of the R&R can cause drops which lower the battery below the R&R setpoint.

In the attached picture you can see my heat sink ground with 3 ring lugs connected to the right screw on the R&R. 1 is the selonoid ground, 2nd is the R&R ground and the 3rd is the common lead directly to the negative side of the battery. The R&R is mounted on top of two 6" sections of 1" copper tubing that was flattened and curved to fit partially around the frame. The frame can be a very good heat sink if you can reduce the thermal resistance. I've see naas much a 40 deg F difference between the R&R and the Frame. right now without heat sink grease I'm down to about 20 degF.

Posplayr

[posplayr]

FYI the fuse box solder job

See attached inside of the fuse box with crimp connectors soldered after using the metal etch.


Posplayr

[brand new bike zealot]

thanks for the ideas. I have the r/r bolted to the frame, but I didn't realise that ground was such a big deal, I was concentrating on the black lead, which I have a direct new ground lead to the baterry on. I'll file up the frame behind the r/r and get a good connection there too.

I'll go over the pos side of the circuit a little better too. Maybe I'll have to replace a the lead to the battery.

If anyone else has been down this road, let me know...

[brand new bike zealot]

just got back from another session with my bike and these are the results.

Took off the r/r, and it checks out fine on the diode test.

Checked the stator for shorts, found none.

Recleaned and wd/40'ed all connections, too lazy at this stage to cut them all for spades, cleaned fuse holder (it is pretty dicey).

Filed down the frame where the r/r bolts on, spritzed a bit of wd on it, and cranked it tight.

Now engine off, my battery is at 12.9, idling at 1400, 13.4, revved to 3000, about 13.6ish drops to about 13.2 above 5000.

This is much better than before. These voltages were measured out of the r/r and at the battery. The battery measured slightly lower.

I think this is now somewhat acceptable, as long as my battery is nice and fresh, and I stick to kickstarting. I may file down the little nub that doesn't let me turn off the headlight so I don't have to run it on a sunny day.

Thanks for the support guys

[BassCliff]

You'll find it in the last place you look

Mr. brand new bike zealot,

Have you performed a continuity check between all three stator wires and ground? There should be no continuity between stator and ground. Even when my "leg to leg" resistance tests were within spec my stator still turned out to be bad. I had eliminated everything else so I figured it had to be the stator. Here's my old stator.



If you like, you can check the pictorial guide documenting my stator replacement on my little BikeCliff website (link in my sig). I basically ended up replacing the r/r (used Honda part from Mr. duaneage), the stator (from RMStator), all the connectors and ran the r/r ground directly to the negative battery terminal. I'm hoping that'll do for the next 20 years. A new AGM battery is next on my list. Good luck and happy wrenching.

Thank you for your indulgence,

BassCliff

[Steve]

Took off the r/r, and it checks out fine on the diode test.

Keep in mind that the diode test only tests the r/, not the /r. That's right, there are two devices in that one shell. The first recifies the AC to a rather sloppy DC waveform. The second then regulates that sloppy DC waveform by momentarily shorting (shunting) any excess directly to ground. That is why you need a good, appropriately-sized wire straight from the r/r to the battery negative terminal. The only practical way to diagnose the regulator part of the device is to verifyy proper operation of the rectifier section (by doing the diode test), then operating it and measuring the results.

I may file down the little nub that doesn't let me turn off the headlight so I don't have to run it on a sunny day.

You may want to do a reality check on that idea. Yeah, I like the freedom of choice, too, but if you still have the old wiring that routes one of the stator legs through the headlight switch, you will disable 1/3 of your charging capacity when you turn off the light. I have checked this on my 650, and found that the output voltage is actually just a bit higher with the light on, because the whole stator is being used to generate power. I do tend to turn the light off when using the electric starter, but will turn the light back on as soon as the engine is running. If you have all three of your stator wires going directly to the r/r, you will notice some extra charging capacity with the headlight off, but please note that the charging system on the bike is engineered to run with a certain load. By decreasing the load, you are increasing how much the r/r has to shunt for regulation (after the battery is charged), so you might be placing the r/r in jeopardy.

This does not even take into account the safety factor of having the headlight ON any time the bike is moving. I am a great proponent of having lights ON, and have gone to the trouble of installing extra lights, as well as a modulator on the headlight and brake lights.


.

[posplayr]

brand new bike zealot

While those voltage are OK for the moment, 8-[ they still suggest that there is about 0.8 volts (minimum) excess drop somewhere. My manual says that the output (1981 GS750) should be between 14.0 and 15.5 volts at 5000 RPM. Using your 13.2V you are between 0.8 volts to 2.3 volts low. That is a high resistance somewhere which is probably corrosion and it is not likely to get any better .

You should measure directly between the R/R output and the battery. If you really want to be lazy then you can probably pinpoint the excessive drop directly across the crimped on bullets and selectivel swap out the bad ones .

It is about 1 hr to swap out the bullet connectos on the stator and the R/R. I think it is 5 pairs.I had all of mine prevously HOT(I just bought the bike so I'm nor sure if it was hard running with lightso ff , on a hot day or what). Everything checked out just not the wiring =;

Posplayr

[brand new bike zealot]

thanks again for all the opinions everyone. I really appreciate the knowledge on this site.

I had no idea about the headlight cutting one leg of the stator curcuit. And yeah realistically, it's kind of a lame idea anyway. It's just easy and makes me feel like I'm sticking it to the man for not letting me choose if I want my headlight on or not.

I think I'll do it right and replace the connectors, new fuse, and see if I can nurse a bit more out of the old girl.

[SPARKSS]

[QUOTE=brand new bike zealot;743639]just got back from another session with my bike and these are the results.

Took off the r/r, and it checks out fine on the diode test.

Checked the stator for shorts, found none.
/QUOTE]
How did you check your stator for "shorts". As referred to by others, a short to ground in one or more stator windings is a very real possibility (and is a typical way they start to fail). Although your line to line voltages might lead you to think your stator works, any short to ground will cause the stator's output to not be rectified correctly and your resulting DC from the rectifier will be low. With the stator leads disconnected, engine running, you should not see any (AC) voltage between any stator lead and ground (chassis) - which would indicate that a short has developed.

[brand new bike zealot]

/QUOTE]
How did you check your stator for "shorts". As referred to by others, a short to ground in one or more stator windings is a very real possibility (and is a typical way they start to fail). Although your line to line voltages might lead you to think your stator works, any short to ground will cause the stator's output to not be rectified correctly and your resulting DC from the rectifier will be low. With the stator leads disconnected, engine running, you should not see any (AC) voltage between any stator lead and ground (chassis) - which would indicate that a short has developed.[/QUOTE]

I didn't do my test with the engine running, but checked resistance between each leg and the ground and it was infinite, or no reading. I'll try with the motor running too. I'll be changing the oil and doing the pickup screen soon, so I may just pull the stator cover and have a look at it. Out of curiousity for the most part.... not sure if I could tell if it's damaged or not

[chef1366]

The fact you have a drop at higher rpms tells me you have a bad stator unless your R/R has a sense wire that isn't connected correctly.

[SPARKSS]

I'd suggest, whenever possible, that you check electrical circuits while-operating (or trying to!) ....... unless the smoke is flying out of something in particular.....even in this case, dividing the circuit to conquer it is still a plan to see the results of your testing in an operating (dynamic) situation. Sometimes, for example, testing a winding, looking for an external path can be misleading if, say, oil or just lack of vibration or heat expansion will look like high resistance on the ohmmeter.....which can change as soon as the machine is running. (not to say this is ineffective......or a good double-check.....just never a good idea for sole reliance!)

My .02 worth....with lots of experience for that bargain price.