Coil swap 650 to 850?

[Guest]

I tested my coils (79 GS 850G) and am getting nothing out of them. Sparks at the points and juice to the coils, just nothing coming through them. Can I swap my 650 coils (80 GS650G) for the purposes of seeing if it will run on them?

[BassCliff]

Hi,

Yes.



Thank you for your indulgence,

BassCliff

[GSNewbie]

Thanks!
Granted the coils are bad as indicated, what is the best replacement? I know a little on dyna but $ 450-500 for a complete ignition seems steep...

[tom203]

Both 850 coils check out bad ?- seems unlikely unless they got cooked. Have you measured the primary and secondary resistance of these coils with your multimeter? primary like 3 to 5 ohms, secondary (caps removed) maybe 12 kohms. Are they leaking hazmat?

[Missile99]

I know a little on dyna but $ 450-500 for a complete ignition seems steep...

Yeah. I doubt also that both coils would croak at the same time. Have you checked all the wiring to them? Also, I can't see ignition replacements costing anywhere near that.

[BassCliff]

Hi,

If your coils are bad (unlikely, but possible) the most popular replacement are the green 3 ohm Dynatek coils. Although, with a points system you probably want the black 5 ohm coils instead. Z1 has them for a pretty good price. If it's just the coils that are bad there shouldn't be a need to replace the whole ignition, just the coils. But test thoroughly before you start spending money.

3 ohm coils: http://www.z1enterprises.com/detail.aspx?ID=210

5 ohm coils: http://www.z1enterprises.com/detail.aspx?ID=1307


Thank you for your indulgence,

BassCliff

[tom203]

If you determine your coils are bad, PM me as I have a set (both 4 ohm primary) off a 82 850- these have the molded in wires with bullet connectors, unlike the 650 coils with spade connectors.

[GSNewbie]

So I did the ohm test for each coil (between plug caps on each coil individually). Ohm meter set to 200k as anything below it just registered "1". Coil 1-4 measured 512k and coil 2-3 measured 30.2

What exactly does this mean? I saw the figure of 20-30,000 ohm being the figure I need...

They do have lots of dirt on them but I don't think it's hazmat?

And they may have been cooked (as in fire). The plastic manifolds where they dump from the carbs into the airbox have been melted. Nothing else looks burned. I will need a new airbox or manifolds.

[tom203]

Coil 2-3 ( 30 kohms ) seems about right-plug cap to plug cap. Best to remove plug caps and check wire to wire-you should get about 12kohms. 1-4 coil could have bad plug cap or poor connection.

[GSNewbie]

Pulled the caps off and tested 1/4 coil with 11.9 ohms. Sounds bad. Why wouldn't I get at least a little spark from 2/3? Any suggestions?

[tom203]

Pulled the caps off and tested 1/4 coil with 11.9 ohms. Sounds bad. Why wouldn't I get at least a little spark from 2/3? Any suggestions?

11.9 ohms??? I think your meter is reading 11.9 kohms-wrong scale on meter?
Since you have points, are they opening and closing? are they connected to coils?

[GSNewbie]

No luck yet

The points are opening and closing when I turn the crank (and sparking).
I tested the coils after cutting off 1/2 inch on each spark plug wire. Ohm meter set to 20k(I can't get readings but "1" on any other setting).
2/3 is now 11.29
1/4 is 12.17
I do now have 12.5V going to the coils.
I tried putting power direct to top of the cap and testing the plug connector inside the cap and couldn't even get the test light to light (strange).

I added a ground wire from the frame to the battery box to see if that made a difference.

I've been reading the manual like crazy. I've tried testing the wires from the points to the coils, but haven't figured out how to do this. I tried a test light and nothing. I'm not sure what to do next?

[Missile99]

I've been reading the manual like crazy. I've tried testing the wires from the points to the coils, but haven't figured out how to do this. I tried a test light and nothing. I'm not sure what to do next?

Take your test light and probe it into the non orange/white wire (the ground wire) at the coil connector while plugged in. I was able to put it into the back side of the connector so as not to damage insulation. Clip the wire of the light to a good ground. Turn your key on. Turn your engine by hand or flick a small screwdriver past the pick-up. If the light comes on your wiring is good. Do this for both coil connectors. If good all around your ignition is working properly and there is something up with coils/plugs/wires.

You have points? I thought it would be signal generator and ignitor for your year.

[GSNewbie]

Thanks! That was easy. I stuck the test light in the black/yellow and white wires and then touched the starter on each was getting signal. Looks like a coil issue (which has been my assumption all along but it's good to check each item off).
I have the 650G sitting here so I guess I can strip them off and try 'em as it's only time doing it...

[Missile99]

The parts list shows you indeed do have a signal generator and ignitor box. Try the test I gave you. If the test light doesn't glow do these tests from BikeCliff's website to find out what the problem is. They are fairly easy.

http://members.dslextreme.com/users/storagecliff/images/electrical_odd-n-ends.html#A11