rough running cold - fine when warm

[tab1324]

When I start my 82 XJ I have a heck of a time sometimes getting it to keep running. I have to keep working the choke lever back and forth a bit and feathering the throttle slightly. It seemed like it was missing on a cylinder or two so I checked the exhaust pipes for warmth. #1 and #3 are cold and #2 and #4 are hot. This is after about 2 minutes of this.... All carb mixtures are set the same. All floats the same. All plugs gapped the same.

After the bike warms up it runs fine on all cylinders but this takes about 5-10 minutes or so. Could it be that I just need new plugs? Could it be something with the ignition? I would think that it isn't carb related because it runs fine when warm. The only difference when cold is using choke.

Any ideas?

Tom B.

[Lloydo]

I have the same problem with mine, ('79 special), and believe it has a lot to do with the intake manifold/boots. Are yours cracked, like they're dried out looking? With the bike running (at it's "rough" point), spray some starting fluid or wd 40 on the boots. If you notice a definite change in how it runs, the boots are leaking air.

[TopCatGr58]

Hey there Tab,

Well, this is a fun problem. Since it's 1 and 3 that are cold, that rules out direct electrical because the coils fire 1-4 and 2-3 combos. The carbs are linked, 1-2 and 3-4 for the supply lines so that rules out the petcocks and lines to the carbs!

However, there could still be problems with the wires from the coils to the plugs/caps, so switching the wires from 1 and 4; and then 2 and 3 would help to eliminate that, cause if the same cylinders stay cold, then the electrical part is good, but if the cold cylinders switch to 2 and 4, then you know it's the plug wires/caps!!

If the electrical checks out, then I'm wondering about the actual choke circuits. Have you inspected the choke linkage/rod that goes to all 4 carbs and the lock screws that connect the rod to the choke plungers to make sure all four are working, and that the choke plunger is actually getting pulled out when you pull on the choke lever?
That's all I can suggest for right now!?
T.C.