Dug into the XJ a bit last night. After 50 miles was pretty sure I was riding a 780cc 3 three cylinder.
Used a high tech diagnostic tool. DIY may not be able to afford this, but WOW is it useful.
a spritzer bottle with plain water. spray on exhaust headers up near the cylinder. Quickly reveals a cylinder that's not pulling it's load. Especially useful on 4 cylinders where it's not immediately obvious who isn't working.
#1- zero heat on the pipe.
pulled all the plugs, WOW plug access on these is awesome easy! Plugs were "new" one was oily... But no smoking. all 4 holes were 160PSI plus,
checked had spark, torch dried the plug ran it, same. Put in a new plug, same. double checked plug caps. resistance good.
Pulled #1 vacuum cap (I'd already replaced all the old cracked caps with new) Sprayed in some carb cleaner, cylinder caught and ran a bit.
Drained some gas from #1 float bowl, gas clean and plenty of flow. Not looking forward to pulling the bank of carbs, #1 is fairly accessable; so....... Pulled, checked, the diaphragm. sprayed carb cleaner down the main jet, pulled checked idle mix screw, tip intact. (@jetmechmarty ) Sprayed more carb cleaner in the idle screw hole, replaced, set at 3 turns out. Pulled the float bowl.
Dang these little guys are handy...
gggGaryized with a bit of rubber fuel line, easier to spin the bit in tight places.
That milwaukee bit set is the bee's knees too.
There was bit of gooey black in the bowl like a piece of fuel line that turned to goo ???
removed pilot. HAH found a criminal, jet was plugged, a bit of fine copper wire, open, reinstalled. Carb back together.
Drained fuel tank, will remove, scrub, clean up, fuel level float assembly, then back together and road test.
More breathless updates later.
Used a high tech diagnostic tool. DIY may not be able to afford this, but WOW is it useful.
a spritzer bottle with plain water. spray on exhaust headers up near the cylinder. Quickly reveals a cylinder that's not pulling it's load. Especially useful on 4 cylinders where it's not immediately obvious who isn't working.
#1- zero heat on the pipe.
pulled all the plugs, WOW plug access on these is awesome easy! Plugs were "new" one was oily... But no smoking. all 4 holes were 160PSI plus,
checked had spark, torch dried the plug ran it, same. Put in a new plug, same. double checked plug caps. resistance good.
Pulled #1 vacuum cap (I'd already replaced all the old cracked caps with new) Sprayed in some carb cleaner, cylinder caught and ran a bit.
Drained some gas from #1 float bowl, gas clean and plenty of flow. Not looking forward to pulling the bank of carbs, #1 is fairly accessable; so....... Pulled, checked, the diaphragm. sprayed carb cleaner down the main jet, pulled checked idle mix screw, tip intact. (@jetmechmarty ) Sprayed more carb cleaner in the idle screw hole, replaced, set at 3 turns out. Pulled the float bowl.
Dang these little guys are handy...
gggGaryized with a bit of rubber fuel line, easier to spin the bit in tight places.
That milwaukee bit set is the bee's knees too.
There was bit of gooey black in the bowl like a piece of fuel line that turned to goo ???
removed pilot. HAH found a criminal, jet was plugged, a bit of fine copper wire, open, reinstalled. Carb back together.
Drained fuel tank, will remove, scrub, clean up, fuel level float assembly, then back together and road test.
More breathless updates later.
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I’m pretty sure if that had been me, I’d have all the carburetors off and on my bench right now, in a million pieces, I’d have ordered $60 in parts and the bike would be down for two weeks. 
Just need to put new o-rings on it, and fashion a handle that matches the threaded hole in the end of the rod.
