Number 3 from left wont fire

[dashingEMT]

After a little oil in the cylinder the compression got to 155. How is it going to free up if the cylinder won't fire. That won't allow the hot/cold process to happen.

[natemoen]

Gonna have to be more proactive about cleaning and swapping plugs. It still heats up even of it isn't always firing.

[crazy steve]

It may not 'free up'; you might just have a worn motor and that's as good as it gets. I suspect you have an ignition and/or carb problem. Do as Nate suggested and swap the 2/3 plug wires; if the problem moves, then you need to look at the coil/wires. If it doesn't move, then I'd look inside the carbs; they may need a good cleaning...

[dashingEMT]

So I cleaned the plugs, and it started firing again. I am now confident the plug is just fouling. Which is great, but after about 7 minutes of idling it fouled again and I lost #3...again. The white smoke was pouring out as well. Not good for neighbor relations!

[crazy steve]

So I cleaned the plugs, and it started firing again. I am now confident the plug is just fouling...

Now you need to find out why the plug is fouling, and I'd start with the carbs. Try tapping on the #3 float bowl; if it's a stuck float, that may clear it. Keep in mind you'll still probably have to pull the carbs and clean them to keep the problem from coming back...

[dashingEMT]

Yeah I am starting to think that way as well. I opened the gap a tiny bit on the plug, cleaned it and started it. Less white smoke, but still a lot. Then I got the classic over rev. Took it around the block...the power I missed was back but wouldnt idle under 3k. As convinced as I was that it wasnt the carb, I am not sure its carb pulling time. Damn things were just rebuilt...oh well.... we shall see. Only have a few more minutes to work on it today then I gotta go play with the wife.

[crazy steve]

These carbs are notoriously hard to get clean; just disassembling them and spraying some carb cleaner around rarely does the trick. You'll find references to 'triple-cleaning' in the post archives, because that's how many times you sometimes have to clean them...

Do check your plug wire/end on the #3 wire; if it's marginal, that could be part of the problem. As to the carbs, the '80-81 carbs use a o-ring seal on the float valve; these seals are noted for leaking if not replaced, so even if the carb is clean and set properly, if that's leaking it will flood out that cylinder. If you don't know if they've been replaced, I would just to be certain...

[Larrym]

Oil Seal Inspection?

dashingEMT,

According to your compression test results the #3 cylinder is a little low. (Little being a subjective term...)

While you are investigating the rings/piston/cylinder as a possible "cause" for the compression loss and source of the "oil/smoke" plus possibly removing the carbs to examine #3 carb for anything wonky:

After removing the carbs take a look through the intake boot of #3 cylinder. Specifically make sure that the intake valve is open. You may have to use an inspection mirror/light source. Look at the intake valve and search for evidence that the valve oil seal is allowing the oil to follow gravity down the stem, onto the valve, and past the edge of the mating surface/lip. (If you crank the engine over first, stick in the inspection mirror, and it comes out with oil spots on it???)

I myself have a leaky valve oil seal on #1 cylinder. Mine seems to only misbehave when I let my XS sit idle for extended periods. It clears up before the engine reaches operating temperature though.

Just reaffirming James England's suggestion to evaluate the valve oil seal 'sall....

[James England]

IMO the most important point here though is the quantity of white smoke which you've mentioned. That tends to indicate the burning of oil usually. There is nothing quite like oil for making huge clouds of white (ish) smoke. Excessive gasoline does not ordinarily do this.... as far as I am aware.....

You've said you verified getting a spark on #3. You have a spark, compression (I don't even know what my compressions are!) and a stuck carb float valve will be obvious if you put the petcock onto 'Prime' and see if fuel drips out all over the place. I presume it isn't doing this or you'd have seen it.

You're burning oil on #3, due to a mechanical fault which, from what you said, occurred suddenly after you'd ridden the bike with no problems, right?

[James England]

I noticed a lot of oil coming out of the right side exhaust

Oil? Or oil smoke? Are you saying you had oil dripping out of the pipe? Just to clarify...... if you actually have oil itself dripping out, then you 100% have a mechanical problem which is nothing to do with ignition or fuel or anything else. 100%

If you mean oil smoke, please see my previous post! ...

[dashingEMT]

There is definitely oil coming out of exhaust. This is why I was thinking rings. The oil pushing past the cylinder....right? Carbs were pulled and are super nice and clean, floats look newish, so it appears they were rebuilt recently. Each time I clean the fouled plug I get about 10 minutes of run time with white smoke (getting less and less now) then the plug fouls and I am back to a 3 cylinder machine.

[Larrym]

S.e.g.?

Each time I clean the fouled plug I get about 10 minutes of run time with white smoke (getting less and less now) then the plug fouls and I am back to a 3 cylinder machine.

But it's a happy ten minutes, right?

[dashingEMT]

There is no time happier than a powerful pig of a bike working how it should!!! But like my wife always says...really...thats all the time I get???

[dashingEMT]

The crazy thing (and all the purests will want my head after this) is that on 3 cylinders it runs plenty strong for me. If it wasnt for the oil coming out of the exhaust and coating my rear tire I really wouldnt care too much...until the whole damn thing blew of course.

[Larrym]

And the point is???

dashingEMT,

Yeah....You only notice that something's really OFF when two cylinders drop out.

So, you're at a point in the process/decision tree. If you really enjoyed the ten minutes you did have then in order to get more ride time something has to be done. I mean everyone here had/has their fingers crossed in the hopes that the problem would "self-heal".

I'm saying that if you do have to go "invasive" then knowing if it's the valve seal or the rings would be useful. If it's the valve seal then the tear down is only to the point of removing the head. (Hah! Notice how I marginalized/trivialized what some view as a rather daunting task...)

What cannot be shunned must be embraced. Just allowing it all to sink in/absorb for ya. Take your time to let all this settle in and afterwards we'll be here to aid in the next steps you decide to take.