one cylinder running...ignition coil keeps shocking me?!

[bfisch1]

So only the left cylinder is firing on my 1981 xs400, for the longest time I thought it was the carburetors and couldn't figure out the problem. Today after trying to start it again for the hell of it I touched the right ignition coil and it shocked me (the non-running side). than the coil hose also has a little spark to the frame of the bike. I figured the coil hose was worn out because it seemed pretty dry rotted so I switched the left and right side but the frame/hose spark still remains on the right. No idea why, anyone have this happen before or have any ideas what I can do?

 

[bcware]

Did you move the coils or just swap the wires connected to the coils around?

 

[bfisch1]

I switched both the coils and wires connected, just left the spark plugs.

 

[bcware]

And the large wire from the coil to the spark plug carp/spark plug is the one arching to the frame?

 

[bfisch1]

Yeah, it gives off a small shock that will arch to anything near it, even the coil itself gave off a shock, not just the wire

 

[bcware]

Does the coil or any of the wires appear damaged or melted?

 

[bfisch1]

The one that gives off the spark is pretty dry rotted, I can't see any bare metal but I can imagine under the extra rubber coating that it's showing somewhere

 

[bcware]

Hm, and you said there is only an arch on the right side of the frame regardless of which coil is hooked up there?

 

[bfisch1]

After I switched them the first time yes, but I tried it three times and 2/3 times the arch remained on the right side, never on the left, I just bought brand new wires from mikesxs for 5 bucks, Ill switch these and hopefully this will fix whatever is happening..any chance the coil itself can be damaged from this?

 

[Tj Gonz]

That was the start of my running on one cylinder problem. I have a mean spark on right side but left is inconsistent. Replaced TCI box, Ignition coils & pick up coils still the same. Try this: If you can get her running on one cylinder pull the weak/dead spark side & hold it about 4mm away from a non painted surface of the motor, Then give it some throttle & check for a mean spark on that side. Thats where Im at right now, Got her idling great but as soon as throttle is applied she bogs & dies..my carbs are prestine
I hope you can find a solution, good luck brother.

 

[bfisch1]

I did that, it gives off a pretty solid arch so there's definitely spark on both sides

 

[METZ]

That was the start of my running on one cylinder problem. I have a mean spark on right side but left is inconsistent. Replaced TCI box, Ignition coils & pick up coils still the same. Try this: If you can get her running on one cylinder pull the weak/dead spark side & hold it about 4mm away from a non painted surface of the motor, Then give it some throttle & check for a mean spark on that side. Thats where Im at right now, Got her idling great but as soon as throttle is applied she bogs & dies..my carbs are prestine
I hope you can find a solution, good luck brother.

I have the same exact problem. No spark on the left side but when you give it some throttle the left side sparks really good than the engine dies. Did you resolve this problem yet?

 

[METZ]

Did you get this sorted out? I've been dealing with the same issue, no spark on the left side. I did find out that the two wires going to the left coil both had battery voltage (it shouldn't) where as the two wires going to the right side coil only had one wire with battery voltage (correct). This was checked with the key on and not cranking over. I guessed that the problem is a bad transistor in the TCI box so I found a used box that was known to be good and the spark is fine on both sides now and the bike runs great. I'm trying to find a replacement transister to fix the old box up for a spare. I don't know if this helps you or not but if either coil has battery voltage on both wires than it probably is the TCI box. I believe it's the Orange and gray wires that shouldn't have battery voltage.

Robert

 

[Jeremy Corbin]

It turns out I'm having the same issue as of today:

I was on the bike earlier today and suddenly it dropped power, like someone turned on an A/C pump. I was at about 4k just cruising around and it just dropped most of it's power.

When I got home I also noticed it was leaking fuel out of the #1 cylinder's exhaust (I found a leak I didn't know I had!) so I checked the spark plug and it's soaked. The #2 cylinder looks normal. I left the spark plug wire off and it didn't change how it ran so at this point I assume that it's only running on #2. One other thing that I noticed is that the #1 wire was trying to spark but it was really inconsistent. I didn't know what to make of it.

Apparently the coils are under the tank but I haven't figured out how to remove the tank yet. Any guidance on this issue would be much appreciated. Those CDI boxes are really expensive! I'm hoping my problem can be resolved without replacing it!

-Jeremy

 

[Jeremy Corbin]

Update for posterity:

I got the tank off and checked both coils against the service manual and they were fine.
I swapped wires and plugs back and forth.
When I swapped plugs I blew the excess gas from the spark plug and it started sparking correctly for a few moments and then started being inconsistent again; fouled I assume.

I figured: If I have spark and I have fuel I must be missing air. Yup. Turns out part of my air filter got sucked into the #1 carb while I was riding. I pulled it all out and cleaned everything back up. It hesitated while starting from #1 plug being fouled but then it came to life. I rev'd it up a bit and it cleared up nicely.

Seems that I didn't have to take the tank off and check the coils, but it was good experience.