Rewiring the battery, stator, R/R and grounds

[hannibal]

Hello,
I just purchased a 77 GS750. I should have spent another hour or two reading these forums, and I would have saved some money. The bike test drove just fine. Got the bike home in a van, and went for a spin. Bike started up and ran fine. I went to start it the next day and got nothing. Checked the battery and saw the positive cable had come off. On closer look, it melted off at the skinny part of the O ring connector. After my first ride, I noticed a bit of smoke but thought it was just steam (it was drizzling). So I'm guessing I have some serious electrical issues, most likely an over charging problem.

I found posplayr's electrical guides and started at the battery. My multimeter is toast (couldn't get a reading and it actually got hot and started to smoke) so I took the battery to autozone. Tested at 12V with no load, but the guy pointed out the liquid inside was moving more like gel. Conclusion: the battery is no good, so I ordered the same battery to replace it. Does this look good?

While I wait for the battery, I'm planning to rewire the stator directly to the R/R using all three wires. I'll also do the common grounding point mod either to the single bolt of the front my 8V 750 R/R (different from the 850 R/R shown in the write up), or to a spot on the frame. I haven't even seen the fuse box yet (under the tank?) but I want to figure something out for the positive side. I'll likely pause and continue posplayr's charging system check once I have the new battery and finish the grounding and stator to R/R rewiring, but before I touch the positive side.

I'm comfortable with the stator to R/R wiring, but what gauge are the three wires coming out of the stator? I bought two sets of spade connectors, 16-14g and 22-18g. I also have some questions about the grounding. How big (what gauge) of wiring should I use for the common ground to negative terminal on the battery? It seems like the other grounds (from the harness, R/R, and frame if I ground to the R/R case) are the smaller gauge (same as the 3 wires from stator to R/R). Is this OK or should I go bigger? I also have a heavier gauge ground from the engine case that went directly to the battery negative terminal. Should this now go from the engine case to my common grounding point?

Two more things: the positive battery to starter relay cable (the one that fried at the battery end) is pretty heavy gauge (10g I'm guessing). Should I go even bigger with this wire or just use the same size as the common ground to battery wire that I asked about above? And lastly, the battery was grounded to the front battery box mounting bolt by a tiny wire. The front bolt goes through a rubber washer and this battery ground (and two other grounds, one from the starter relay, not sure about the other) were attached between the bolt head and the rubber washer. Is this how it came from the factory?? No wonder it has grounding issues!

I also want to say thanks for such a great forum. There is so much info here. I was kicking myself for paying for a bike that was supposed to be "ready to ride" but turned out to have these electrical issues. But with the info here, I'm confident I can update the wiring, then diagnose my charging system and get this thing running. Any harm to the bike to kick start it and ride it without a battery attached to the wiring? Can't wait to get this thing on the road...

Thanks!

[chucksuki]

Yup, came from factory grounded like that. I can answer a few of your questions: I like fat grounds so I usually use a slightly larger wire. Your bike likely doesn't have a fuse box, just a single inline fuse between the R/R and battery. You are right to relocate the grounds. I highly encourage you getting the wire schematics for your bike and studying it hard. Stator goes to r/r, r/r goes to bike and battery. A couple new grounds and you are headed in the right direction. You do, however, have quite a bit more elbow grease you are going to have to rub on that bike before you have a truly dependable machine. 2 main points to attack, fuel system and electrical system. Replacing all connections on the bike is also not a bad idea.

[chucksuki]

Oh, don't run the bike until you get that wiring figured out. Battery or not, when you fire that baby up those wires go live

[tom203]

"Any harm to the bike to kick start it and ride it without a battery attached to the wiring? Can't wait to get this thing on the road..."

leave your tired battery in, or disconnect stator from rectifier and regulator. Otherwise your regulator will not be happy!

[G-3]

I look at that main fuse, the previous owner might have put a in bigger one in or just hotwired it in some Fashion!
Mine turned out to be too low voltage and I kept popping it until I figured out it was incorrect size!

[posplayr]

When I make the SPG harness for the SSPB, I crimp together 3 wires in a single oversize (10-12 AWG) ring lug; one 14 AWG and two 16 SWG. You end up with

all wires are collected to the SPG crimped and soldered.

The R/R(-) to SPG should be 14 AWG with and the open end soldered directly to the R/R (unless you have a final connector for the SH-775).
The Battery ground has a ring lug on it and is 16 AWG.
The Frame ground has a ring lug on it and is also 16 AWG.

You could make them all 14 AWG but that makes the SPG crimp a little harder.

The final ground is a B/W ring lug from the harness. I just stack it on top of the SPG with a little dielectric grease. This ground has nothing to do with charging so it is OK to just stack it and not try and tie it into the same 3 way crimp.

And as mentioned do not run the bike without a battery, the R/R will connect your electrical to rectified AC which can go upwards of 30-50 V depending upon load and RPM.

[chucksuki]

The man himself! Follow what posplayr says and you can't go wrong. That's what I did and now I have 2 REALLY great bikes that are as dependable as the day they were built! Btw posplayr, Thanks a million for being incredibly helpful

[posplayr]

The man himself! Follow what posplayr says and you can't go wrong. That's what I did and now I have 2 REALLY great bikes that are as dependable as the day they were built! Btw posplayr, Thanks a million for being incredibly helpful

Thanks for the props

[hannibal]

Thank you for the replies, and thanks to Jim for his write ups and help.

Made some good progress this weekend. I replaced the connectors on the 3 wires between the stator and R/R and taped off the old wires to the headlight switch. Made new battery and frame ground wires and merged these in a big ring lug. I stacked the big ring lug with the R/R ground on the single R/R mounting bolt. The R/R ground wire is quite short and I didn't want to cut off the existing ring lug to merge it with the battery and frame grounds. The wires are sealed into the unit so I'm not sure the cleanest way to extend it. I think I'll leave it like this to begin testing the charging system. If I need to replace the R/R, I'll redo the SPG. My mounting bolt was too short to add in the ring lug on the B/W harness ground so this is grounded higher up on the battery box. I correct this as soon as I find a bolt.

Question: In my earlier post, I used the term "engine case ground" to refer to the heavy gauge wire from above the transmission to the battery. Can this serve as my frame ground? This is the "frame ground" I merged with the battery ground at the SPG.

I've been studying the wiring diagram and took a look at the positive side on my bike. Current on the left, planned on the right:


I couldn't see where the two red wires from the R/R and starter relay intersect, but I found continuity between the wires. The fuse is a glass type (didn't read the size) covered in a plastic case. At some point, a fuse melted a hole in the case. I mentioned earlier that the positive cable on the battery had melted off. The other end on the starter relay seems to have been 95% melted as it broke off at the ring lug as I poked around. The factory wiring diagram shows the fuse on the R/R leg, not the battery side. I just looked at the wiring diagram in Jim's GS Charging System Health pdf. It shows a 15A fuse on the battery leg. Can I ask why you would fuse the battery side but not the R/R side?

I'm planning to pick up a new style inline fuse holder and charge the battery for the first time. Aside from straightening out the new fuse, I don't think I'll touch the positive side until I go through the charging system checks.

[posplayr]

Thank you for the replies, and thanks to Jim for his write ups and help.

Made some good progress this weekend. I replaced the connectors on the 3 wires between the stator and R/R and taped off the old wires to the headlight switch. Made new battery and frame ground wires and merged these in a big ring lug. I stacked the big ring lug with the R/R ground on the single R/R mounting bolt. The R/R ground wire is quite short and I didn't want to cut off the existing ring lug to merge it with the battery and frame grounds. The wires are sealed into the unit so I'm not sure the cleanest way to extend it. I think I'll leave it like this to begin testing the charging system. If I need to replace the R/R, I'll redo the SPG. My mounting bolt was too short to add in the ring lug on the B/W harness ground so this is grounded higher up on the battery box. I correct this as soon as I find a bolt.

Question: In my earlier post, I used the term "engine case ground" to refer to the heavy gauge wire from above the transmission to the battery. Can this serve as my frame ground? This is the "frame ground" I merged with the battery ground at the SPG.

I've been studying the wiring diagram and took a look at the positive side on my bike. Current on the left, planned on the right:


I couldn't see where the two red wires from the R/R and starter relay intersect, but I found continuity between the wires. The fuse is a glass type (didn't read the size) covered in a plastic case. At some point, a fuse melted a hole in the case. I mentioned earlier that the positive cable on the battery had melted off. The other end on the starter relay seems to have been 95% melted as it broke off at the ring lug as I poked around. The factory wiring diagram shows the fuse on the R/R leg, not the battery side. I just looked at the wiring diagram in Jim's GS Charging System Health pdf. It shows a 15A fuse on the battery leg. Can I ask why you would fuse the battery side but not the R/R side?

I'm planning to pick up a new style inline fuse holder and charge the battery for the first time. Aside from straightening out the new fuse, I don't think I'll touch the positive side until I go through the charging system checks.

Using the engine as the frame ground is probably not going to hurt anything but I wouldn't do it. If the currents in the engine are trying to get back to the SPG before returning to the R/R(-) the most likely path of least resistance is for those engine currents to go past the battery on that big 6 awg cable. So lets say you have a Dyna S and it ground through the engine you now have those 3 amps running past the battery to get back to the SPG. Battery charging currents do not really exceed 4 amps so with the Dyna-S current wired this way you now have the voltage drop of 7 amps between the battery and SPG where if you went to the frame you would likely pick that 3 amps up and not route it past the battery. The less current going from battery(-) to the SPG the better the charging. When is good enough? You are trying to keep your voltage drops low. I like less than 0.1V but the limit in the stator pages is 0.25V. What ever it is it is reducing your 14.5V regulator setpoint by whatever the drops are at the battery reducing the charging. So in effect you are violating the SPG when you do it by sharing frame currents with battery currents before they get to the SPG.

The battery has to be fused because if it shorts you will melt wires. The most likely way to blow the main fuse is a shorted R/R. The R/R can only output 20 amps at most so it doesn't need to be fused before the individual fused circuits.

[jbird7262]

Stupid question.......SPG ?

[posplayr]

Stupid question.......SPG ?

Single point ground

[hannibal]

Thanks Jim. I think I understand your explanation about the engine ground. Are you saying the ground from the ignition (through the engine case) would want to travel back to the battery through the big wires instead of going through the smaller R/R negative wire? If this is the case, I will ground the engine case to the frame (I'm using a 9AWG wire), and run a smaller (14AWG) wire from the SPG to the same spot on the frame. Does this look better?


As for the fuse on the positive side, the 8V GS750 only has the single fuse (from what the wiring diagram says). I haven't seen a fuse box like on the GS850. I was thinking it would be best to fuse the R/R side because that's where all the power comes from when the bike is running. But you're saying to put it on the battery side to protect the system from the battery. Would you still recommend this without a fuse box after the ignition switch? Ideally, I'd like to add a fuse box and separate circuits in the future, but this will likely be months away. I don't even know how I will accomplish this.

Thanks again for your help. I should be able to pick up my new battery today. Add a day to charge and I'm hoping to start it up tomorrow.

[hannibal]

I can't seem to edit my post so I'll an this FYI: the engine ground cable originally ran from the engine case to the negative terminal on the battery, which sounds like the worse thing to do!

Also, using the 9AWG wire because that's all I had. I ordered some 14 AWG wire just in case...

[posplayr]

A couple of quick comments:
The engine is bolted to the frame is various places. Except for dirt and grime it is going to be hard to improve upon that with a ground strap. In fact you might create a sneak path for the starter and fry something. I would NOT do it.

I assume what you have labeled as SPG R/R is in fact the R/R with a mounting bolt used for the SPG. That being the case I don't know why you need a heavy wire from the battery. That Should carry 4 amps at most if just charging and maybe 7 amps if you have a DynaS. Do you have a Dyna S?

NO MATTER what, if you short your battery it will supply many many amps melting wires. So no matter what fusebox or single fuse you have you better fuse the battery as close to the battery as is practical. There is nothing more to be said. If you want fuses in other places, fine, but if you ever have a R/R short and there is no fuse you will regret it.




This is a standard configuration with allowance for various numbers of wires from the R/R. If you realize that all current has to return to the R/R(-) , then it should be clear that the SPG is the collection point for all of those current before the final run to the R/R(-). The SPG is collecting any frame currents, B/W currents and finally the battery charging currents. The only thing to be careful of is that the battery wire only carries charging currents, however in practice this might be hard to do when there is a large 6 -8 AWG starter grounding strap to the back of the engine.
Generally the ignitor does not ground out to the engine, but the Dyn S does. There is probably nothing you can do about that it is going to return via the ground strap right past the battery and share current with battery charging currents exactly what you don't want it to do. But alas there is nothing you can do short of running a separate ground wire to the plate of the DynaS. Is it worth it? Probably not.
If you had a clamp on amp meter you could test all of this and much of the mystery would go away.

What are you doing different and why? I'll try and answer those questions .