Coil relay mod on a GS750E

[pdqford]

I'm ready to do the coil relay mod on my 1980 GS750E, but I'm hesitant to start snipping the wires in my strickly stock harness without some reassurance from the BTDT members.

I didn't want to snip the wires on the coil pigtails thinking that if I ever have to change a coil it would be nice to be able to just plug and play the replacement coil.

So here's my plan (before I cut anything ): I will snip the orange/white stripe wires between where they come out of the main harness but before the coil connectors.

One of the O/W wires coming out of the harness I'll connect to the control side of the relay (#85) and I'll ground the other side of the control relay (#86).

The other O/W wire coming out of the harness I'll tape off.

The other side of the snipped O/W wires leading into the coil connectors I'll wire in parallel to the power out terminal of the relay (#87).(And I'll feed #30 of the relay from the BAT + through a fused wire.)

Is this a good way to make the mod? Or am I just being paranoid and I should just make the cuts at the coil pigtails (which would leave my main harness unmolested)?

Okay - easy now

[Guest]

I'm ready to do the coil relay mod on my 1980 GS750E, but I'm hesitant to start snipping the wires in my strickly stock harness without some reassurance from the BTDT members.

I didn't want to snip the wires on the coil pigtails thinking that if I ever have to change a coil it would be nice to be able to just plug and play the replacement coil.

So here's my plan (before I cut anything ): I will snip the orange/white stripe wires between where they come out of the main harness but before the coil connectors.

One of the O/W wires coming out of the harness I'll connect to the control side of the relay (#85) and I'll ground the other side of the control relay (#86).

The other O/W wire coming out of the harness I'll tape off.

The other side of the snipped O/W wires leading into the coil connectors I'll wire in parallel to the power out terminal of the relay (#87).(And I'll feed #30 of the relay from the BAT + through a fused wire.)

Is this a good way to make the mod? Or am I just being paranoid and I should just make the cuts at the coil pigtails (which would leave my main harness unmolested)?

Okay - easy now

Just curious why you are doing the relay? I've had my 750 since new and was getting a good solid 12 volts to the coils. I just recently during my renovation pulled the wires and redid the ends to the coils. Then again I have had the Accel super coils since 83. Seemed like the stock coils were getting weak for some reason even thought they were getting 12 v as well. When I put the Accels on, the motor felt much better.

[pdqford]

Just curious why you are doing the relay? I've had my 750 since new and was getting a good solid 12 volts to the coils.

Good question. When I started this major tune up (three years ago ) I was reading ~10.8V volts at the coil connector. I've been cleaning connectors and switches with Detoxit (sp) and polishing grounds and installed a new AGM battery the other day. Now with the battery at 12.8V I'm getting 12.2V at the coils.
Since I already acquired the parts for the coil relay I thought I would just do it and be done with it. But space is tight.

I think the real issue is the R/R. I've acquired a SH775, but will save those questions for another thread. First I want to get the ignition as good as it can get so I can sync and adjust the carbs (which have recieved the full strip & dip treatment).

[spyug]

If you have 12+v at the coils, you don't need to do the relay mod as, at best, you will only pick up .6v and likely not even that. What you have already is excellent. The relay mod is recommended if you are only able to achieve 11v or so at the coil. Don't waste your time.

Now what's the probs with the R/R? If that's not working properly then you'll have more serious issues to deal with.

[pdqford]

If you have 12+v at the coils, you don't need to do the relay mod as, at best, you will only pick up .6v and likely not even that. What you have already is excellent.

Maybe then I should hold off on the relay mod. Just don't want to have to get in there every year or so and clean up all those connectors.

Now what's the probs with the R/R?

On a good day it will only put out 13 - 13.2 volts. I put a used R/R in there about 15 years ago and it seems to be getting tired. The diodes seem to be okay with a forward bias, but I can't check the yellow one as the regulator seems to be in the path.

The stator appears to still be good as it puts out 73.2 VAC between any pair of stator leg pairs at ~5000 rpm. (Thats from my notes as I just hung the carbs on there and they need to be sync'd.)

Thanks you for your comments.

[posplayr]

Maybe then I should hold off on the relay mod. Just don't want to have to get in there every year or so and clean up all those connectors.


On a good day it will only put out 13 - 13.2 volts. I put a used R/R in there about 15 years ago and it seems to be getting tired. The diodes seem to be okay with a forward bias, but I can't check the yellow one as the regulator seems to be in the path.

The stator appears to still be good as it puts out 73.2 VAC between any pair of stator leg pairs at ~5000 rpm. (Thats from my notes as I just hung the carbs on there and they need to be sync'd.)

Thanks you for your comments.

Do the revised Phase A tests in my signature under GS charging heath and report back here.

[pdqford]

Do the revised Phase A tests in my signature under GS charging heath and report back here.

Aye-eye sir. Reporting as requested:

Voltage @ battery @ 2500 rpm = 13.3 volts
Voltage @ battery @ 5000 rpm = 13.4 volts

Positive lead voltage drop @ 2500 rpm = .35 volts
Positive lead voltage drop @ 5000 rpm = .78 volts

Negative lead voltage drop @ 2500 rpm = .04 volts
Negative lead voltage drop @ 5000 rpm = .04 volts

Based on the positive lead voltage drop, perhaps I can just wire the R/R positive lead right to the battery + and be good to go.

I also see that I still have the third leg of the stator running up through the headlight switch. (I thought I changed that years ago, but apparently decided not to. ) Since I didn't have the headlight on it was prolly running and charging with only two legs. I'll bypass the headlight switch and re-run the numbers.

[Steve]

I also see that I still have the third leg of the stator running up through the headlight switch. (I thought I changed that years ago, but apparently decided not to. ) Since I didn't have the headlight on it was prolly running and charging with only two legs. I'll bypass the headlight switch and re-run the numbers.

You actually have a functioning headlight switch on your '80?

I know that some bikes still had the switch, but its function was blocked, leaving the light on all the time.

.

[pdqford]

You actually have a functioning headlight switch on your '80?

Actually, I removed the block many (30? ) years ago, thinking I could charge the battery faster if the headlight was off, not realizing that turning the headlight off would also eliminate one leg of the stator.

(Everything seemed so simple when I was younger. )

[posplayr]

Aye-eye sir. Reporting as requested:

Voltage @ battery @ 2500 rpm = 13.3 volts
Voltage @ battery @ 5000 rpm = 13.4 volts

Positive lead voltage drop @ 2500 rpm = .35 volts
Positive lead voltage drop @ 5000 rpm = .78 volts

Negative lead voltage drop @ 2500 rpm = .04 volts
Negative lead voltage drop @ 5000 rpm = .04 volts

Based on the positive lead voltage drop, perhaps I can just wire the R/R positive lead right to the battery + and be good to go.

I also see that I still have the third leg of the stator running up through the headlight switch. (I thought I changed that years ago, but apparently decided not to. ) Since I didn't have the headlight on it was prolly running and charging with only two legs. I'll bypass the headlight switch and re-run the numbers.

Hopefully you now understand why when people post that they have 13.5V at the battery at 5K RPM why I say there is a problem . i have even seen experienced members here say it is OK.

You can also see why I revised the Phase A test to test at 5000 RPM when there is the most current flowing. The voltages are higher from the increased current at 5000 RPM. In many cases at a low idle speed there is no current going to the battery (all to the electrical system) and so there is no voltage sensed giving the wrong conclusion using the original test.

If you add the 13.5V at your battery plus the +0.78V across the positive leads you get 14.28V which is just at the specified regulation point for the regulator.

If there is 5 amps of charging current then you are wasting about 4 Watts in the wire/fuse box alone. A plastic fuse box doesn't like that much heat and they will melt when the metal contacts get hot which commonly causes shorts between circuits..

The hidden killer ( if you were using a SHUNT R/R) is that the extra current that should be going to your battery to get it up from 13.5V up to 14.25V is being shunted in the stator. This is not an Issue with a Series R/R. If it is confused with bad connection it opens up.

You can usually get rid of these drops by cleaning your fuse box with naval jelly and soldering the internal contacts if it is the bulb type of fuse holder. The newer style doesn't need that. You should do this and I generally don't recommend connecting the R/R directly to the battery.

And yes I know everybody does it.



I see now that you have a 1980 GS750 which is very much like the 1981 GS750E I used to have. Here is a picture of the back of the fuse box.

Disconnect the battery, pop the back of the cover off and lift up the crimps part of the way. You don't want to stress them too much by lifting too far.and liberally apply the naval jelly. Let it sit for 5 to 10 minutes and wash it off with water .Solder

Those crimps and put it back thew way you found it. It will probably fix most of the problem.

[pdqford]

Since I didn't have the headlight on it was prolly running and charging with only two legs. I'll bypass the headlight switch and re-run the numbers.

Here's the numbers:

First number is two leg with headlight off.
Second number is with three leg and headlight off.
Third number is three leg with the headlight on.

Voltage @ battery @ 2500 rpm = 13.3 volts/13.6 volts/13.4 volts
Voltage @ battery @ 5000 rpm = 13.4 volts/13.9 volts/13.6 volts

Positive lead voltage drop @ 2500 rpm = .35 volts/.43 volts/.58 volts
Positive lead voltage drop @ 5000 rpm = .78 volts.55 volts/.99 volts

Negative lead voltage drop @ 2500 rpm = .04 volts/.03 volts/.06 volts
Negative lead voltage drop @ 5000 rpm = .04 volts/.03 volts/.08 volts

The excessive voltage drop on the positive lead from the R/R goes through a connector to a splice inside the wiring harness, then back through another connector to the fuse block, through the fuse block, its glass fuse and connectors up toward the battery which has another connector and then a splice where it joins the battery + cable ring.

Why is it that I shouldn't run the R/R + straight to the battery and bypass all this stuff?

[posplayr]

Here's the numbers:

First number is two leg with headlight off.
Second number is with three leg and headlight off.
Third number is three leg with the headlight on.

Voltage @ battery @ 2500 rpm = 13.3 volts/13.6 volts/13.4 volts
Voltage @ battery @ 5000 rpm = 13.4 volts/13.9 volts/13.6 volts

Positive lead voltage drop @ 2500 rpm = .35 volts/.43 volts/.58 volts
Positive lead voltage drop @ 5000 rpm = .78 volts.55 volts/.99 volts

Negative lead voltage drop @ 2500 rpm = .04 volts/.03 volts/.06 volts
Negative lead voltage drop @ 5000 rpm = .04 volts/.03 volts/.08 volts

The excessive voltage drop on the positive lead from the R/R goes through a connector to a splice inside the wiring harness, then back through another connector to the fuse block, through the fuse block, its glass fuse and connectors up toward the battery which has another connector and then a splice where it joins the battery + cable ring.

Why is it that I shouldn't run the R/R + straight to the battery and bypass all this stuff?

Because that is not how it was designed, and you will have to run a larger fuse than 15 amps to accommodate that"NEW" configuration. So if you want to do that go ahead.

If you have a "T" (as designed) then the current between the battery and the electrical separates there. If you don't (as you propose) then you are passing all the current to both the battery and the electrical from R/R to battery.

[pdqford]

Because that is not how it was designed, and you will have to run a larger fuse than 15 amps to accommodate that"NEW" configuration. So if you want to do that go ahead.

If you have a "T" (as designed) then the current between the battery and the electrical separates there. If you don't (as you propose) then you are passing all the current to both the battery and the electrical from R/R to battery.

I'm not gonna run the R/R + straight to the battery - just was trying to understand why some do when I've seen you post that you are opposed to doing it that way.

I've had the back off the fuse block to clean up the contacts when I was trying to increase the voltage at the coil. Guess I will have to get some navel jelly to polish them up and add a little solder.

I did find something interesting when I was chasing parts of circuits with my ohmeter to pinpoint just where the resistance was hidden. Resistance between the negative battery cable ring and any place on the engine was ~.2 ohms. (I had cleaned and polished the connection where the negative battery cable bolts to the engine case.)

But the resistance between any bare spot on the frame and the negative battery cable ring was 1.1 ohms. I've cleaned up a number of grounds for the Blace/White stripe wire that runs through out the harness, but they always ground to the frame. If I take a reading between a bare spot on the frame and a metal surface on the engine it reads .6 to .7 ohms. I don't know if the engine is mounted in rubber or if where it mounts to the frame are paint covered, but shouldn't there be something like one of those woven ground straps to ground the frame to the engine, or at least to the negative battery post?

[posplayr]

I'm not gonna run the R/R + straight to the battery - just was trying to understand why some do when I've seen you post that you are opposed to doing it that way.

I've had the back off the fuse block to clean up the contacts when I was trying to increase the voltage at the coil. Guess I will have to get some navel jelly to polish them up and add a little solder.

I did find something interesting when I was chasing parts of circuits with my ohmeter to pinpoint just where the resistance was hidden. Resistance between the negative battery cable ring and any place on the engine was ~.2 ohms. (I had cleaned and polished the connection where the negative battery cable bolts to the engine case.)

But the resistance between any bare spot on the frame and the negative battery cable ring was 1.1 ohms. I've cleaned up a number of grounds for the Blace/White stripe wire that runs through out the harness, but they always ground to the frame. If I take a reading between a bare spot on the frame and a metal surface on the engine it reads .6 to .7 ohms. I don't know if the engine is mounted in rubber or if where it mounts to the frame are paint covered, but shouldn't there be something like one of those woven ground straps to ground the frame to the engine, or at least to the negative battery post?

You can clean all those other grounds but the only ones that will affect your charging voltage are between the R/R and the Battery. I reviewed power and grounding here

http://www.thegsresources.com/_forum/showthread.php?t=140109

so if you read that you will see I am trying to separate out all currents that do not go to the battery and run don't run them between the battery and the R/R. By doing that you reduce the current and therefore any voltage drops due to resistance will be less. That is the objective and the way Suzuki did the plus side of the power distribution is correct although I suspect it was by accident.

Also the R/R doesn't need to be fused as it will only put out 15 amps anyway. The battery does need to be fused because in a short it will deliver much more.

[pdqford]

Woooie!

You can usually get rid of these drops by cleaning your fuse box with naval jelly and soldering the internal contacts if it is the bulb type of fuse holder.

I poped the back off the fuse block again. Still looks like new in there. But I went through and soldered each wire crimped connector in there! And polished the tabs which contact the glass fuses.

Now I don't want Pos to get too excited, but here are the numbers after soldering these perfectly crimped connections:

These numbers are with all three legs of the stator working and the lights off:

Voltage @ battery @ 2500 rpm = 13.9 volts
Voltage @ battery @ 5000 rpm = 14.1 volts

Positive lead voltage drop @ 2500 rpm = .27 volts
Positive lead voltage drop @ 5000 rpm = .30 volts

Negative lead voltage drop @ 2500 rpm = .02 volts
Negative lead voltage drop @ 5000 rpm = .02 volts

And am now reading 13.3/13.4 volts at the coil connectors!
I'm Happy

Don't know why the resistance netween the negative battery cable ring and the engine case is .2 ohms while the resistance from the same cable to the frame is a whooping 1.1 ohms !

Maybe I should run a grounding strap from the engine case to the frame?