79 GS750 wiring no battery

[Steve]

..., the stock wiring diagram would be very helpful IF i didn't have Dyna ignition

The Dyna ignition changes very little, in regards to the wiring.

In the stock wiring, power goes to both coils, then a wire from each coil goes to one of the two sets of points, then to ground. With the Dyna setup, power goes to both coils, then a wire from each coil goes to the Dyna module, which is then grounded. The only real difference is that the Dyna module also requires a power wire.

I looked at your diagram (as requested), but had a hard time reading it. From your description of power flow, "stator>regulator>spst key switch > capacitor> fuse box>ignition wire, master lights switch, and brights switch", I have to question the capacitor. What are the values and how is it wired? References to electric guitars mean nothing to me, I have never dealt with them.

On the ignition side, you mention your electronic ignition module you say you have a white wire going to the points. If you have installed electronic ignition, you should not have any points.

Finally, I will have to ask the same question I have asked many others that have tried to go this route: what is your motivation to ditch the battery?

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At the risk of sounding like I just want someone to tell me what to do, and avoid researching anything, I'm hitting alot of dead ends in figuring out the wiring. I have heard people tell me the stator is electromagnetic and needs a battery, I have seen diagrams with more or less wires coming from stator, regulator, ignition, or points than I have on my equipment, i have seen diagrams with no electronic ignition, and the list goes on... I have searched endlessly for a diagram that reflects what i need and is credible with no luck. I simply need someone to look at my diagram and tell me whats right or wrong. All I am trying to do is get a spark, but I need to know my wiring is good even if it is only theoretically. the stock wiring diagram would be very helpful IF i didn't have Dyna ignition

[Brendan W]

I think you're about ready for this

https://www.thegsresources.com/_forum/showthread.php?171846-Top-10-Newbie-Mistakes

Measure twice cut once is as true for old bikes with unknown history as anything else and you will save a lot of time and money in the long run by going at a project methodically. There is no end of helpful and better informed people on here who will lend a hand in a heartbeat to any one who wants to do it right.
This is our library, complied and uploaded fro the benefit of anyone prepared to read and learn.

http://members.dslextreme.com/users/bikecliff/

My guess as to what happened to fry the wire was very poor wiring but this might just be wishful thinking. the bike has been owned by three people before me who thought themselves to be a bit more handy than reality. the carbs were disassembled, but they never reassembled them or even bothered to buy a rebuild kit, the seat was replaced with a hideous fiberglass monstrosity with the cushion bolted on (talk about a pain in the a**), and the wiring harness looked like freddy kruger got inside a bikers dream and tortured him by working on his bike

I have the wiring as stator>regulator>spst key switch > capacitor> fuse box>ignition wire, master lights switch, and brights switch

the lights are pretty straight forward, but the ignition wire i have going to the coils and the electronic ignition, the negative side of the 1-4 coil goes to the tach and the electronic ignition, and the negative side of the 2-3 coil just goes to the electronic ignition. from the electronic ignition i have a ground and a red wire, a black wire, and a white wire going to the points.

Now that you mention that i looked at some schematics again, and the capacitors clearly are grounded, for some reason I hadn't noticed this, and thought they ran in series (probably because thats how electric guitars capacitors are wired). just had one of those ah-ha moments followed by feeling a little dumb for not picking up on that earlier... I guess thats why i'm here though

Thanks for your help Brendan, I am so thankful to be able to take on these projects during a time where the technology exists to be able to get help from people all over the world, and even more grateful that people such as yourself exist to help others, out of nothing more than passion and a desire to pass on their knowledge

[Brendan W]

Nominally a 10A fuse will handle 120 Watts. For a standard headlight and tail etc this should be ok.
However you have LED lighting which reduces the load.
Now you may have another problem.
The stock charging set up relied to an extent on lighting load to take some of the output. Now that is not being used you have more pressure on the system to find places to dump the excess and you don't even have a battery to help out. A solution for this excess problem is to replace the stock shunt regulator with a series regulator. This is what I and many others have done even with a battery to protect the stators.
Fried wires are easy to replace. The question is why did it fry on such a low current part of the harness.
And yes, a capacitor is pretty pointless with a battery installed.

Also curious if the grounds are better on the motor than the frame, or are they both equally adequate? is 1 10a fuse is enough for all the lighting? I know 1 10a fuse was what the factory ignition system had, but is 1 10a what I would need for the Dyna ignition setup(potentially a question for dyna)? is the capacitor relatively pointless with the battery, or could it still be beneficial in the circuit? lastly when i was working on wiring the points, i noticed a wire (the black from electronic ignition to the points i believe) looked pretty oxidized/fried, and did not want to take any solder, is this a wire I can replace? is this a sign of a problem with something in the ignition?

[Brendan W]

Is there a capacitor is series with the key on the top right of the schematic?
DC will not go through a capacitor.
What I know about running bikes without a battery could be written on a matchbox but that capacitor looks all wrong.
It should be in parallel with the rest of the system in the same way that a battery would be.
A battery is amongst other things a capacitor. I smooths the regulator output as well as storing charge.

Have a look in our library for ideas about educed harnesses, testing and links to other harness ideas

http://members.dslextreme.com/users/storagecliff/images/electrical_odd-n-ends.html#A09

When everything is sorted you can always ditch the battery at that point.

theres a thought! although im also partially just trying to save some money, so i might just keep it if I get one. I would still like to avoid getting a starter motor if I can, from what I've seen this shouldn't be an issue, what do you think? it seems like I can just put the battery + where I have the capacitor (after the regulator and before the key switch), and add a ground on the negative side.

I tried to upload the schematic again, but can't upload it any larger than the first, is there someway to upload that any larger? if not would you be comfortable pm'ing me your email so I can send you the schematic? i am fairly confident it should work, but a second opinion from someone more knowledgable than myself would be greatly appreciated.

thanks a bunch Brendan

[Brendan W]

Sorry can't read the wiring diagram.
I think you cannot rely on a capacitor to have enough charge to do meaningful tests. Get a battery. They weren't called accumulators for nothing.
To check the stator output the bike needs to be running with the stator disconnected and the battery is what keeps the ign supplied while you do checks. Stator output between any two should be near 80 Volts AC at 5000 rpm
When everything is sorted you can always ditch the battery at that point.

[switchback_bomber]

got a gs750 project and need another perspective to get spark, thanks in advance for any help you can give me

the bike came with no starter and a demo'd wiring harness. I decided to make a wiring harness from scratch with no battery. I have a stock stator and rectifier. the coils, ignition, and points are from dyna. I have an spst switch for the brights, and another for all the rest of the lighting to cut off power to everything other than the ignition while i am kicking it over. I'm using 1 10a fuse for the ignition, and another for all the lighting. I'm also using a capacitor, and LED lights so they won't be quite so dim at low rpm's.

I have a schematic I drew up and attached it to show you what all the wiring looks like. Hoping someone knows a bit about these bikes and can let me know what could be causing a problem in getting spark if it is identical wiring to the schematic.

tested the coils (6ohm ea), regulator (1-4.5 v), stator(but only one of the three wires and it was giving out 2.35 v), and lastly i tested the points, but was having trouble getting more than a momentary ohm reading.

I'm noticing nothing coming from the capacitor, but after kicking it like a tweaking mule i was getting 5-6.5 volts from the capacitor to the ground, but after leaving it be for 10 minutes it went back to putting out nothing. I had the ignition hotwired during and after doing this, so i'm not sure if that would drain the capacitor when it has a full circuit, or if it would do this regardless. tomorrow i'm going to test each stator wire, and make sure there all evenly putting out volts.

past the stator potentially being an issue, or the hotwiring potentially being a problem for the capacitor, do you guys see any potential issues with the wiring? are my numbers sounding reasonable? should I just get a battery and stop being stubborn about running it without one?