weird problem

[ergojack]

I changed the plug wire, then later, swapped the coils & wires with an extra set I have.  Still the same problem

[racerrad8]

I changed the plug wire, then later, swapped the coils & wires with an extra set I have.  Still the same problem

Then you have it narrowed down to fuel.

Just because the bowl is full doesn't mean it is flowing through the jets into the engine. Look for the fuel spray when you crank the throttle and raise the slide.

Randy - RPM

[Bones]

About the only thing I can think of that hasn't been mentioned is your ignition module. Maybe it developed a fault somehow where its sparking at the wrong time on No 1 cylinder.    Cap'n Ron had trouble on his epic trip where his bike developed a problem with starting and was backfiring. Turned out the module chucked a wobbly inside where all the magic happens and changed the timing so it was about 180deg out. Randy sent him a spare one, plugged it in and he continued on his way with no futher trouble.

[FJ_Hooligan]

Take that can of carb cleaner over to your running lawn mower and spray it into the intake.  The engine will instantly DIE.  

Try it again using a STARTING fluid. 

[ergojack]

Randy, It has fuel when you accelerate the engine & the slide rises. 
I tried introducing starting fluid to see if that would make a difference & it did not.
I have swapped the coils & wires with an extra set I have.  No change.

[ergojack]

If the ignition module was bad, wouldn't that also affect cyl. #4 as well since they share the same coil?

[racerrad8]

I know someone else asked what the plugs looked like earlier.

Can you snap some photos of the plugs in the order removed from the engine?

Randy - RPM

[Flynt]

I am stumped.

Had been riding my 84 FJ1100 about 10 or 12 miles, when it suddenly started skipping and sometimes backfiring through the exhaust.
I rode home & started checking it out.  I found that while holding the throttle steady at 2,000 RPM, & pulling off the plug wires,
all cylinders would cause a RPM drop & stumble except for #1, which had no change.  Switching plug wires #1 & #4 had no change. 
Problem is still on #1.  I checked & then replaced all 4 spark plugs - no change.  Spraying fuel (carb cleaner) directly into intake #1
through the vacuum port had no change.  Compression test showed 120 on #1, 120 on #2, 110 on #3 & 110 on #4.  Pressurizing
#1 cyl. with air pressure revealed no air leaks from intake or exhaust.  Pulled the valve cover & checked the cams, valve clearance &
operation of the valve train. No problems found.  I have an extra set of coils, so I put them on just for the heck of it. No change. 
What's up with this bike?

Jumping back to the top on this...  it came on suddenly makes me think electrical, but I think you've worked that out and (other than trying a new controller) have swapped most everything anyway.  A sudden fuel thing would be a clog or something breaking in the carb.  The only "break" I can think of that might cause something like this would be if your choke plunger moved somehow?  Have you checked out the choke linkage?

Frank

[Bones]

If the ignition module was bad, wouldn't that also affect cyl. #4 as well since they share the same coil?

They might share the same coil, but the igniter box lets the coil know when to send a spark, so if something has gone amiss somewhere, well, who knows. You said #1 cyl has spark, but is it sparking at the right time. 



Actually thinking about it more, I think the FJ has a wasted spark system where #1 and #4 should fire at the same time, so if that's the case ignore the above

Either way, Do you know of anyone with a spare that you can try, that way you can rule it out altogether. You've tried everything else.

[ergojack]

Success!! - mostly
I put the bike completely back together so I could ride it and get a plug reading.
Ran like crap until I got off the pilot circuit and into the needle circuit.  It now runs
strong with no skipping as long as you are in the needle or main circuits.  The only thing
that has changed since I last rode it, is pulling the carbs & checking the jets. I now
know the problem is a fueling issue in the idle/pilot circuit of #1 carb. 
Before when I rode it, the bike skipped all through the RPM range and under any type
of load.  When the problem 1st started, I was cruising around 50 MPH when it suddenly
started skipping.  I don't know what changed, but at least I know where to focus now.
It also will idle smoothly now at 1050-1100 RPM. As soon as you start off, the skipping,
bucking, etc. starts until you can get up to some speed. It would not even idle at all before.