81GS650L Spark Plug Wire Connections / Firing Order

[DaveP]

Staring another thread for my misfire issues with a different question and hopefully this might be the solution rather than believing that I didn't do a good job cleaning and rebuilding the carburetors.

I think this is probably what is going on, but want to double check that I made a newbie mistake that no one has thought of yet.

When I got the bike, many components were removed including the spark plug wires, so I didn't have a chance to see how things came apart. Spark plug wires had their original labels, so the left pair had labels 1-3 and 2-4 I believe with same on the right coil, so I connected the two on the left to cylinders 1 and 2 and the two on the right to cylinders 3 and 4.

Only half my connections are correct according to this link: https://answers.yahoo.com/question/i...3100637AA4R7w2

Signal generator wiring diagram in the service manual would suggest the same except for my lack of understanding.

True?

[Steve]

I think this is probably what is going on, but want to double check that I made a newbie mistake that no one has thought of yet.

Very small chance of that.

Now, to answer your question:
The cylinder order is 1 through 4, of course, with #1 on the left (under your clutch hand) and #4 on the right (under your throttle hand).

The firing order is 1 - 2 - 4 - 3.

Unless someone has gotten "creative" with the wiring, the coil on the left will fire plugs 1 & 4, the coil on the right will fire plugs 2 & 3.

When you connect the left coil to the plugs, it really does not matter whether you connect #1 or #4 lead to the #1 plug. Electrically, they are the same, but one lead might be an inch or two longer, so send it to the other side of the engine. Same thing applies with the right coil.

.

[DaveP]

Thanks Steve. That should explain why only half the engine is running

Now I need this work day to end so that I can go home and try this out.

Next confession, the two different size spark plug boots. Two short ones were on the left side and two longs on the right side. I thought someone else must have screwed that up before not having mixed pairs on each coil.

One of the longs was definitely bad, spring missing between the electrode and resistor??, and I have replaced them with NGK boots. Hopefully the leads are long enough for the cross-over to number 4 now..., but I'll still need to reposition two of the boots. 102° and 120° bends on the new ones.

[Skinner]

Hi Dave,

Here's a pic from my 1981 650GL. It's not the best but you can see the left coil clearly. The left wire from the coil is going to cylinder 1, while the right wire goes under the frame tube to cylinder 3. The right coil fires 2 and 4.

[DaveP]

Kevin, Your GS650L is coming along nicely. I have been following your posts since you are a few steps ahead of where I am with the same bike. Not sure mine is going to clean up as nicely.

Just to clarify, should you have said 1 and 4 from the left coil and 2 and 3 from the right coil?

Your photo shows what I had for spark plug boots and would have had the two long boots coming from the right coil for cylinders 2 and 3.

Thanks,
Dave

[Skinner]

Kevin, Your GS650L is coming along nicely. I have been following your posts since you are a few steps ahead of where I am with the same bike. Not sure mine is going to clean up as nicely.

Just to clarify, should you have said 1 and 4 from the left coil and 2 and 3 from the right coil?

Your photo shows what I had for spark plug boots and would have had the two long boots coming from the right coil for cylinders 2 and 3.

Thanks,
Dave

Crap. Sorry Dave. My brain was thinking one thing, the hands were typing another. Left coil 1 & 4, right coil 2 & 3.

Monday. Bah.

[DaveP]

WOW! Really runs well when you put the spark leads to the correct cylinders. 45 minutes from start of swapping leads, vacuum syncing carbs, and setting the idle back to 1,100 RPM.