XS1100 Triple

[LoHo]

I started the beast up with the intention of checking the pick-ups and maybe tuning the carbs, but secretly hoping that she had somehow healed and that all would be well. She started right up and idled okay, still with the occasional spit. I listened for the spit to figure out if it was intake or exhaust. As I pondered that, I held my hand near the pipes as they heated up...and one wasn't getting hot. Old Number 3, of course. Also, I figured out that the spitting was on the #3 intake side. The plug was black, but not fouled out. #3 has good compression and good spark. A different spark plug yielded the same results. Could it really be so rich that it won't fire? And could it be too lean to fire without showing a lean plug?

[motoman]

I started the beast up with the intention of checking the pick-ups and maybe tuning the carbs, but secretly hoping that she had somehow healed and that all would be well. She started right up and idled okay, still with the occasional spit. I listened for the spit to figure out if it was intake or exhaust. As I pondered that, I held my hand near the pipes as they heated up...and one wasn't getting hot. Old Number 3, of course. Also, I figured out that the spitting was on the #3 intake side. The plug was black, but not fouled out. #3 has good compression and good spark. A different spark plug yielded the same results. Could it really be so rich that it won't fire? And could it be too lean to fire without showing a lean plug?

....not if it's black too after plug change. If all else is what you stated, fuel level in #3 is likely too high.

[DiverRay]

LoHo,
you will need to pull the carbs again. I would check the "O" rings on the inlet valves. #3 may have pinched and is leaking, and the cause of the problem you are having with the carbs. This is just a guess, and as good as any other, but worth the check, IMHO. I LOVE my '78/'79 carbs, and have yet to pull carbs on the '80MNS for a reason. I think the "O" ring is one of those things that should have NEVER BEEN.
A good test is pull carbs, "C" clamp to a board so they are about the same as mounted on the bike, and put a fuel tank onto one pair of carbs at a time. Once you know the leaking carbs for sure, pull float bowls from that pair, mount carbs upside down, and put gas to the pair once more. If the "O" ring is bad, you will see the gas leaking. I know, work get's in the way of the testing.....