Question on coils

[KDS111]

Hello all,
I fired up the GS850 today, it only ran on two, maybe two and a half cylinders. The two outside cylinders were not firing. The left side was making a weak attempt and the right was doing nothing. Wiring is clean and intact, no damage. I'm wondering if the coils need replacing, or could it be something else. If it is coils, anyone have a working set to sell?

[KDS111]

Bump Bump Bump

[Agemax]

swap the 2 coils over, see if the problem transposes to opposite cylinders. if so that proves a duff coil. if not its an ignition system malfunction

[Rover]

You could reverse the coils and see what happens.

[Nessism]

I suggest you check voltage at the coils. Harness resistance often knocks down voltage, then spark follows. The stock GS coils are very reliable and rarely fail. If the coil voltage is low, you either need to clean the harness connectors (not very easy) or perform the relay mod.

[KDS111]

I'll check the voltage at the coils after work and report.
I see there are a couple of ways to do the coil mod.
Can you recommend the best option?

[Steve]

I see there are a couple of ways to do the coil mod.
Can you recommend the best option?

For me, the 'best option' is to clean the connections and leave everything stock, but others appear to not be so lucky.

To determine whether you would benefit from the 'coil mod', turn the key ON, check the voltage at the coils AND at the battery.
If they are more than a volt different, try cleaning the connections first. If that does not get the voltage necessary, go ahead and do the mod.

.

[Zig's GS]

Hello all,
I fired up the GS850 today, it only ran on two, maybe two and a half cylinders. The two outside cylinders were not firing. The left side was making a weak attempt and the right was doing nothing. Wiring is clean and intact, no damage. I'm wondering if the coils need replacing, or could it be something else. If it is coils, anyone have a working set to sell?

The problem might also be carb related! Swop the coils out and if there is no change, check the carbs for fuel.

[Maddevill]

Er...

Not having any spark will not be carb related.

[salty_monk]

Note that one coil controls 1&4 cylinders & the other 2&3.

[Zig's GS]

Note that one coil controls 1&4 cylinders & the other 2&3.

Which justify my statement of the carbs. Surely if the coils were bad they would be bad in matching pairs 1&4 and 2&3.
Maddevil, I did not see the part where he mentioned it does not have SPARK

edit: I read it again and it seems they are bad in pairs. Sorry!

[KDS111]

Cylinders 2and 3 fire fine. Cylinder 1 is spotty and 4 is dead.
To test the voltage at the coil you just put the volt meter across the primary side of the coil? Which way is the best way to do the coil mod? I see there are different ways. I still have to swap the coil wires.

[KDS111]

The battery voltage is 12.9.
The voltage at both of the coils is 8.6.
Swapping the wires on the coils, it will not run.
What should the next step be?

[Agemax]

8.6v is not enough for your coils. either run through all the connections to rectify this or do the coil relay mod.

[KDS111]

Understood. Can you supply a link to the coil relay mod.
I've there are a couple of versions. What is the best way to do this.
It makes no sense that the voltage is the same for both coils but the outside cylinders are flaky.