spark only on cylinders 1 & 3

[underground]

Hey made a thread a few days ago but my situation has changed. Hope that's okay.

So I'm only getting a spark on cylinders 1 & 3 -- 2 & 4 don't fire. Weird seeing as how 1 & 3 are on different coils. I'm ordering new spark plugs and caps. Is there any other reason this might happen??

Thanks.

[underground]

Oh yeah and it's a 1981 gs650e. For those unable to read my mind.

[spyug]

As I mentioned in your last post, check your plugs and plug caps. Most likely the plug caps. If one lead has spark, the other does to and the only thing stopping it would be broken leads (unlikely) and or worn plug caps (very likely) or worn out plugs (also very likely).

First, change one of the good plugs for one that is not sparking, if still no spark then its the plug cap.

Spyug

[argonsagas]

Hey made a thread a few days ago but my situation has changed. Hope that's okay.

So I'm only getting a spark on cylinders 1 & 3 -- 2 & 4 don't fire. Weird seeing as how 1 & 3 are on different coils. I'm ordering new spark plugs and caps. Is there any other reason this might happen??

Thanks.

Yes, bad wires.


They can break internally, especially if the PO used automotive radio-resistance wire which is prone to that problem.

Check for continuity with a light or meter. If still in doubt,, and since you are already replacing the plugs and caps, replace the wires as well.

[koolaid_kid]

Before you toss the wires or caps, trim ~1/2" off the end of the wires. Look at the copper in the center of the wire. It should be bright and shiny. If not, trim a bit more, I prefer 1/4" at a time at that point. They tend to oxidize over the decades, and need a fresh connection. Then reattach the caps and try again. You would be surprised.