Coil relay mod

[cyberdork]

Alright did some more research and finally understand it, just needed a better diagram. Only bad thing is I'm going to Aruba for a week so I'll probally forget about it lol. As soon as I get back I'm getting the bike inspected and on the road, so I don't know if I should risk doing this before inspection or not.

[Macmatic]

I just bought and tried a 4 terminal relay, same results. I didn't think the relay was the problem since 87 & 87a both had no voltage until the relay was energized and 12v+ as soon as I switched to RUN.

I asked this over in tech info but never got a reply: It isn't going to hurt the coils to hook the positive directly to the battery positive and make momentary contact between the neg and battery negative, right? I tried that with a '95 Kat coil the other day and didn't get anything although it seems like it should be a good coil. I don't see how this could fry a coil unless 1/2 second or so is too long, I never grounded it for longer than that.

Does the coil need to be grounded to the frame via the mounts to work?? I had this coil free of the bike and only connected to the wiring +/-.

This SHOULD have given me a nice fat spark I think. For comparison and to make sure I wasn't seeing it as worse than it really is I just pulled the plug from my line trimmer and checked that spark. It looked WAY better, nice and blue and fat where the bike spark is blueish, thin and hard to see. Maybe I should rig up a couple of Stihl coils!

Maybe its time to spring for a set of Dyna coils? I've been meaning to do that for a couple of years but she always ran so sweet I never got around to it.

I have another set of GS750ES coils and at least one set each of '82 GS650 and GS550 Kat coils to dig up and try first....won't be ordering new coils for at least a paycheck anyway.

Thanks for the input,
/\/\ac

[doctorgonzo]

If these are original stock coils, the wire or the cap could be the source of the weak spark instead of the coil. Just a thought.

[Macmatic]

Breakthrough

So now that I discovered this I remember reading it in manual but until now I never picked up on this and no one in either thread had asked an important question.

I only had one plug per coil grounded, grounding the second plug made a major improvement in the spark It still isn't the fattest spark I've seen but it looks acceptable and many times better than the weak sauce it was before.

Tomorrow I'll try starting and running again... I hope the coil mod makes a difference, I had pretty good voltage with the stock wiring. I think I only gained about .3v but thats for another thread.

Thanks for the help everyone!
-/\/\ac

[horror1972]

Coil relay mod

It isn't that hard, a relay:

85 is ground and 86 is any positive power.
this 2 terminals are the coil of the relay, or the electronic switch.
you can feed 86 from about 9 to 14 volts.
30 is the input, and 87 the output, so it doesn't matter what's on the 30 terminal, the only thing it does is connect 30 and 87 when the coil is activated; 78a works the opposite; when the coil isn't activated,it's connected with 30, and when the power is on 86, it disconnects.

so what you do with this mod is using the o/w wire from the killswitch to switch the coil (86) and get a fresh battery power from the 30 terminal at 87.
unless you have bad wiring or a bad killswitch, it doesn't make any difference.

hope this make sence.

[Macmatic]

It isn't that hard, a relay:

85 is ground and 86 is any positive power.
this 2 terminals are the coil of the relay, or the electronic switch.
you can feed 86 from about 9 to 14 volts.
30 is the input, and 87 the output, so it doesn't matter what's on the 30 terminal, the only thing it does is connect 30 and 87 when the coil is activated; 78a works the opposite; when the coil isn't activated,it's connected with 30, and when the power is on 86, it disconnects.

so what you do with this mod is using the o/w wire from the killswitch to switch the coil (86) and get a fresh battery power from the 30 terminal at 87.
unless you have bad wiring or a bad killswitch, it doesn't make any difference.

hope this make sence.

Thanks for the input but it turns out that wiring wasn't the issue. My main problem was that I didn't know I needed to have both plugs from a given coil grounded to have good spark. Given that I probably never had a spark problem in the first place and I only picked up .3v by doing the coil mod and never found any resistance in the wiring over .4ohm this has probably been a waste of troubleshooting time. But hey, at least now the coil mod is done and I can get back to figuring out my dead cylinder issue.

86 has to be switched power so the coils aren't always energized, 30 has to be +12v from the battery, fused.

87a is not the same on all 5 pin relays! Two of mine have a different diagram and 87 & 87a function exactly the same. I also have a 5 pin with two 87 connections, the 87&87a relays I tried work just like the one with two 87 terminals.


/\/\ac

[cyberdork]

I'm hoping for a quick response for this so if anyone knows please let me know! Anyway...does anyone see any problem with using 12 gauge all the way around, I've always been told to match the ground and power wires, and also I'm not sure if I have the right relay. Mine looks like this...Dorman #84601

[80GS750]

12 gauge wire should be ok... as long as its thicker or the same as the stock wiring you will be ok.

and yes that relay should work just fine

[cyberdork]

Note to self: never use liquid electrical tape again....PITA

[cyberdork]

problem



Can I join the orange wires together and connect them to my wire going to 86? And will my starter be inside the engine cover?

[cyberdork]

Crap forgot which side of the coils is which wire

[kingofvenus]

Crap forgot which side of the coils is which wire

Light grey is coil 1/4

[cyberdork]

Well it turns over but its not firing. I took both orange wires on the coils and joined them together along with the wire going to the relay. I think it might be they way I wired the starter. I hooked the wire from the relay to the top nut of the starter assuming that was the positive wire on the coil. Help!

[Macmatic]

Well it turns over but its not firing. I took both orange wires on the coils and joined them together along with the wire going to the relay. I think it might be they way I wired the starter. I hooked the wire from the relay to the top nut of the starter assuming that was the positive wire on the coil. Help!

Did you plug everything back in? I know I didn't....twice. First I left of the signal wires at the igniter box and then later I forgot to re-attach the new ground for the relay when I was moving wiring around.

Mine is done and ready to take out for a shake down run now but looks like it'll be right after work tomorrow or Thursday. I'll have to post back a pic of the wiring! I think it came out pretty good.

/\/\ac

[cyberdork]

alright here's the way I did it

-ground to a frame point
-1 wire that goes from the relay to the top point of the starter
-1 wire that goes from the relay to BOTH of the orange white wires off of the coils
-1 wire that goes from the relay to the positive sides of the coils

I used a multimeter and turned the bike on and checked for voltage from the starter wire, but did not get any readings, so my guess is the starter....? But common sense tells me I shouldn't get anything from the starter until I push the ignition button. I'm severly disappointed that I've spent a little over 20 dollars on everything to have it all fail.