Performed ignition relay mod today...

[modular]

....and I picked up 1.3 volts. Before I started I checked the battery voltage. It was 12.6 volts. I then checked the O/W coil power wire with the negative battery terminal. That was 10.3 volts. After the relay mod it went up to 11.6 volts. Does this sound about right?

Bike idles slightly better, the exhaust has a slightly different tone...below 4k RPM I can hear each cylinder firing with a deeper note. Sounds really good and obviously pulls a little harder. It may be that the packing is getting broken in in the new V&H Megaphone, who knows. Did the 1.3 volts really make that much of a difference?

Bike in question is my '77 GS750.

 

[Steve]

Did it make a difference? It depends.

When you measured that 11.6 at the coil, what was the voltage at the battery? :-k

If the battery was also at 11.6, your coils are now seeing "full" voltage. If the battery was showing about 12.5 or so, you still have some problems.

11.6 at the battery might be "normal" with a battery that is not quite fully charged, and then has the load of the bike's headlight and coils imposed on it. After a full charge, the battery should settle in at 12.6 to 12.8 volts. It should drop a few tenths when you turn the key ON, then drop some more when you activate the starter, but should not drop below 10 volts. If it does, you need a new battery.

 

[modular]

Battery was at 12.6 between the posts. This was after sitting for over 24 hours since last ridden. It is a new(er) battery. The only lights that were on were the neutral and oil pressure light in the gauges. The job was done with all new wires from the relay forward and I tapped into the "on" position wire in the kill switch after the plug where it goes into the main harness behind the headlight. 11.6 at the coils is still unacceptable?

 

[BassCliff]

Hi Mr. modular,

It seems the modification you performed has helped. Mr. Steve is correct in that once the mod is in place you should get full battery voltage at the coils. Have a look at the coil relay mod information on my website to double-check your work.

Coil Relay Modification
(by Mr. oldryder and Mr. Matchless)

More On Coil Relay Modification

You have only 2 posts? I thought you'd been around longer than that. What happened to the rest of your posts? Just in case, please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thank you for your indulgence,

BassCliff

 

[modular]

I used one of the mounting bolts for the airbox as my ground. Was that a good choice?

 

[SqDancerLynn1]

That 1.6 volts will make a difference. You will get a stronger spark and better cold starting..

 

[Steve]

Would that be for the ground to activate the relay? No problem.
If you turn on the key and the relay clicks, you have chosen a good ground.

What is more important is your power path. Should start at the battery or the battery side of the starter solenoid. Electrically, they are the same spot. I use the solenoid to minimize the number of wires at the battery terminals. From there, you should have a decent-size wire (at least 16 gauge) going through a fuse to the #30 terminal on the relay. From the 87 terminal, you should go to both coils. Very few connections, all new wires, you should have very close to battery voltage at the coils.

.

 

[modular]

Even before the mod I was having absolutely no cold start issues. The bike is running well. The biggest difference(but not that big) I noticed after the mod was the idle. I have the power picked up at the starter solenoid with on in-line fuse holder, the two coil wires connected to the Dyna S power wire and the power wire coming from the new relay. All said wires had to be connected to the pigtail socket I bought to go with and plug into the relay.

 

[BassCliff]

Hi,

I'm using the bolt that holds the rear master cylinder to the frame as my ground for the coil relay, aftermarket flasher unit, and secondary ground for the r/r unit (7-wire unit).

These are my connections under the tank.

Thank you for your indulgence,

BassCliff

 

[modular]

Yep, just like I have mine except I have the Dyna S power wire attached at the coil wires as well. I assume #86 attached to the wiring harness in the above picture is the "on" position pick-up from the kill switch. I just hooked mine up at the headlight with a new wire ran to the new relay.

 

[BassCliff]

Hi,

Oh! Dyna-S hardware too? You got me there. But Mr. posplayr has something for you...

Dyna-S Coil Relay Mod
(by Mr. posplayr)


Thank you for your indulgence,

BassCliff

 

[modular]

The '77 GS's don't have igniter boxes, do they? I actually saw that write-up after I did the mod but it did not make much sense to me. The write-up on your website had everything I needed. Just not sure where the 1 volt drop is coming from. That check was made at the connection of the coil power wires and the power wire coming from the new relay. Maybe the extra connections from using the socket and not wiring the connections directly to the relay is making a difference. Was the 10.3 volts I was getting before really all that bad? Guess I will see how it affects my mileage which is about 34 MPG all city driving.

 

[Matchless]

I have the power picked up at the starter solenoid with on in-line fuse holder........

You should have full battery voltage at the fuse holder and then at the coils when ignition and killswitch is on.
If you have used an inline fuse holder with a tubular glass fuse, I would suggest getting rid if it as they make bad contact and can easily fail, especially the aftermarket bayonet car radio type.

 

[modular]

I used a seal-able blade type fuse holder as I have seen pictured here. I actually did not check voltage right at the fuse, just where I connected the wire from the relay to the orange coil wires.