Stator wire that goes to headlight switch before R/R?

[Chuck78]

My 77 GS750 seems to have a newer regulator/rectifier installed, but my wife's is still the original setup. I'm wanting to try out a Series style R/R on both of our bikes after reading about how most of them work (shunt style), as hers is original and mine is low on output (stator checks out good).

On hers, one phase is still the original wiring which sends the AC voltage direct from the stator through the headlight switch, and back to the regulator/rectifier where the other 2 stator ouput wires are already connected respectively.

What was the purpose of this wire, and can I just send the three stator wires straight to the R/R like how my 77 GS750 was wired when I got it? Just looking at hers, I would think the headlight runs on direct AC volts or something, but that seems very odd... I read one other post saying that those two wires to and from the headlight switch can just be abandoned, that they are unnecessary and can just be snipped and taped off, that they were just added there to put extra resistance in the circuit.

I am puzzled and seeking a deeper understanding of why this was there, and what to do if I wire the stator direct to the R/R. Is this some sort of cut off that just turns off one phase when the headlight is off? I thought that one phase of the stator was unregulated, according to reading up on the stator papers. Maybe this occurs internally to the R/R?

[Chuck78]

Also, what years had separate regulators and rectifiers? Looking at the Clymer's wiring diagram, it shows the separate voltage regulator just tied into one leg of the three phase output direct from the stator. Neither of our 77 models have this setup anymore fortunately. From reading that the original suzuki units had left one phase unregulated made me expect to see two wires off the stator being sent to the regulator, not one! Does this still translate to one phase only being left unregulated? just trying to understand the basics of these electronics.

[barnbiketom]

on some early models, the headlite switch could be turned off. I 'think' one of the reasons for that loop was if the headlite was off, it also cut one one phase of the stator, supposedly to reduce overcharging, but as I see it , it only made the stator run hotter since all the magnetic field went into TWO outputs instead of one.. bad idea huh?

[Steve]

on some early models, the headlite switch could be turned off. I 'think' one of the reasons for that loop was if the headlite was off, it also cut one one phase of the stator, supposedly to reduce overcharging, but as I see it , it only made the stator run hotter since all the magnetic field went into TWO outputs instead of one.. bad idea huh?

True, and not so true.

The switch for the headlight actually had two sets of contacts. One set provided the current to the headlight, the other one was the third leg of the stator. The concept was that when you turned the headlight OFF, you would also disconnect one third of the stator's output so the R/R would not have to shunt as much to keep the voltage regulated.

The stator would not run any hotter. Each leg of the stator is completely separate, and couldn't care less how many others were in the circuit. "Magnetic field" simply exists, it is not forced into anything. Since the stator was not generating as much current, it would actually tend to run cooler overall, not hotter.

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[barnbiketom]

True, and not so true.

The switch for the headlight actually had two sets of contacts. One set provided the current to the headlight, the other one was the third leg of the stator. The concept was that when you turned the headlight OFF, you would also disconnect one third of the stator's output so the R/R would not have to shunt as much to keep the voltage regulated.

The stator would not run any hotter. Each leg of the stator is completely separate, and couldn't care less how many others were in the circuit. "Magnetic field" simply exists, it is not forced into anything. Since the stator was not generating as much current, it would actually tend to run cooler overall, not hotter.

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gotcha!!!
so it's kinda like in any circuit, if it is not complete, then there is no current flow, and the lower the resistance, the more flow.
That said, why do some say that LED lites , or any kind of lessening on the system load will have no effect on the overall stator's load?? I can see where the rect/reg shunts voltage all the time, but this is hard for me to fathom.

[Steve]

That said, why do some say that LED lites , or any kind of lessening on the system load will have no effect on the overall stator's load?? I can see where the rect/reg shunts voltage all the time, but this is hard for me to fathom.

That is because, with the permanent magnets in the rotor, the output of the stator (not the whole system) will simply increase with engine speed.
Anything that is not used by the bike will have to be shunted to ground to regulate the voltage.

If you lessen the load, you will simply have to shunt more current to ground.

If you want to maximize efficiency, you will actually want to increase the load right up to the point where the load balances the output, so the regulator does not ever have to shunt anything to ground. The problem with that is when you shift gears, the engine speed will change, meaning that your output will change, so you will need to change your load, too.

On a car or a bike with a variable-field alternator (not the permanent magnet systems that we have), you can lessen the overall load with LEDs and it will make a difference.

One last fly in the ointment: unless you want to spend about $300 for an LED headlight, you are only going to change the tail/brake light, turn signals and instrument cluster lights. The instrument lights don't draw all that much to start with, you won't save much by going to LEDs. The turn signals aren't on that much of the time, so you won't be saving much be going to LEDs. The only light that will make much of a difference would be the tail light. The stock bulb is 2 or 3 watts, an LED replacement will be between 1/2 and 1 watt. Consider that each of your coils has about 4-5 ohms of resistance, so will draw about 3 amps each, or about 40 watts each, for a total of 80 watts. The headlight is rated at 55 watts. Just to keep the bike going, you are going to be needing about 138 watts, including the tail light. Change that light to an LED, you would only need 136 watts.

But they LOOK really nice.

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[Normk]

All good information.

Question of the OP though: What is your intent? Do you wish to reduce heating of the VRR with the attempt to prolong life or to have more power available for other uses such as quicker recharging, bar heaters...?

The ignition load won't be quite as high as stated because the current flow is not continuous and induction will cause a current lag but Steve knows that so was likely just using that as an illustration. If you wish more power for other loads, you may wish to pick up a couple of amps by installing a 35 Watt HID unit. I've done this on many bikes in order to improve lighting, make the bike more visible, and to decrease headlight draw.

Just in case some of the above is useful.

[Steve]

The ignition load won't be quite as high as stated because the current flow is not continuous and induction will cause a current lag but Steve knows that so was likely just using that as an illustration.

True enough, so let's get just a little more detailed.

He has a bike with points, so they are open for a few degrees of crankshaft rotation. I have not seen dwell angles published for these bikes, but will assume that it's about 50 degrees. That means that the points will be open for 50 degrees of crankshaft rotation, and closed for 670 degrees. When the points are closed, current flows through the coils to saturate the magnetic field. When the points open, the magnetic field collapses and you get a spark at the plugs.

Looking at the numbers, the points are open about 7% of the time, closed for 93%. Using the rough numbers from above (40 watts per coil), you will still need to provide about 36 watts per coil (72 total), 55 watts for the headlight, 3 for the tail light, and a couple more for all the little dash panel lights, you will still need just a little over 130 watts.

By the way, I made sure to note that his bike has points. For the newer bikes that have electronic ignition, the current flow is interrupted for a much shorter amount of time, meaning that they will need just a little more current than a bike with points. Add in the fact that the coils have lower resistance (more current flow), you will actually need even more current.

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