Ben While, new issue(s)

[FM-USA]

My 1991-I hasn't needed much attention in a few years. Good thing but now I'm chasing a surging issue (idle to 2,000-ish RPMs) that so many have had, has struck me. Did the usual mechanic in a can in the fuel, didn't work. Oil & filter changed 1K ago.
For starters, carb cleaner squirt the usual places for vac leaks, none.

Pulled spark plug cap 1 by 1 & listened for RPM drop, all consistent, was time for new NGK plugs anyways. It has a consistent pesky slight weak cylinder miss at idle, above 2K it's smooth (idle circuit fuel delivery?). Runs stronger but no change on the surging. Wasn't expected to fix it, they were due. Oddly at idle & off-idle it sound's like one spark plug is weak. That miss-beat is still there & consistent. (oops, repeat)
Did the 'Toothpick trick" and that unknown cylinder 'miss' is gone.

Noticed a dried fuel puddle in the fuel tray petcock's area & tightened the 4 screws, no more drips = temp-fixed. I was in there, new clear fuel filter.
Pulled the carb side hose & drained an ounce+ of fuel & refilled with Zep Carb-Cleaner. Pyroil changed their formula & it doesn't work as well. Ran the engine until it started to stumble then 1/2 doz quick accelerator pumps (A.P.) then turned it off. Dinner time, let the cleaner do it's job. Returned 45 mins later, ran the cleaner out, surging still there... DARN! was hoping. Back flushed each A.C. nozzle with carb cleaner for that just in case. Each nozzle is clear with equal squirts BUT not the usual full hard squirt I'm used to seeing.

Pulled the Carbs & went through all the Vac lines in the carb area, replaced 2 that were 'IFFY' but were not an issue.
Remembering the A.C. squirts were a little weak I open that up as well. The spring was like new, the diaphragm had no holes but was a little stiff from old age. (Jumping ahead... I bent the A.P.'s arm a smidgen to eliminate the dry pump at the beginning of it's throw. no more ever so slight hesitation on take off.

Long nose pliers I wiggled each coils 2 connections, felt solid & tight with no residue under each connection.

Reinstalled the carbs and the surging is still present but it's now contained to at idle. It's now ride-able with smooth take-offs from stops.

3 other possibilities & looking for input before diving back into this Wing.
1.) Temp sender on the R-intake, it's OEM. QUESTION: Any KNOWN lesser expensive sensors that work? $50-ish is a huge dent these days.
2.) One weak coil plug wire? Currently unknown is they're wire or carbon filament. These wires are cut to exact length so trimming 1/2 inch off at the plugs won't work if they're carbons. Ol-farmers trick, if they're carbons I'll insert an inch paperclip in each end.
3.) ??? YOUR INPUT ???

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[FM-USA]

3.) ??? YOUR INPUT ???

4.) 75 lookers and no input???

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[ct1500]

By observing a consistent RPM drop with plug wires removed one at a time those can be ruled out for the time being. The accelerator pump does not come into play during idle so that can be ruled out too. By covering the idle air bleed in the carb throat and the surge going away points to a lean condition in the idle circuit of the carbs. Is it one, the other or both carbs when idle air bleed is covered that the idle improves and surging stops? If the MC has been setting with old gas I would be going straight to the idle jets. Check to be sure the slide(s) in the carbs are not stuck open.
Pinch off or cover the large shot air and pulse air intake hose underneath air box at right front noting any change in running. It is possible too that the air jet controller is stuck open bleeding air into idle circuit causing the problem. That can be checked by removing hoses from carbs at controllers and placing your finger over open ends or simply pinching them off with pliers noting any change. Those few things are where I would start.

[FM-USA]

I ride year round so fuel has zero chance to go stale, most it ever sat was maybe a week.

Did all those & the only item that might be a clue is the plugging of each idle air bleeds. (R) one does near nothing while the (L) improves smoothness a lot. I've carb-cleaner back flushed both so I know they're clear.

Both diaphragms & sliders are working just fine and in sync. Finger pushing back has the same resistance and no binding.

I posted the accelerator pump for those who have similar issues at take-offs for a possible EZ fix.
I know it has nothing to do with surging issue BUT doing that makes the bike more ride-able with instant squirts.

I think my next move will be pulling the carbs top plate off and see if the O-Rings are intact.
Then pulling them again & peeking in the 2 bowls & see what's hiding, if anything.

LASTLY and open to anyone who knows...
Has anyone successfully minimized the vacuum hoses on these Wings?
I know there's 3 circuits for smooth throttle but we've lived with minimal hoses until early 1970s when GOOBERMENT stuck their nose in our business.

THANKS

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[ct1500]

So the problem is the left side. Check the No.4 intake runner horizontal vacuum line, pinch the hose off there to confirm no downstream vacuum leaks by observing for any change in idle quality. You might have a vertical vacuum hose off the No.6 intake runner, do the same there. It is possible the pilot jet for that carb picked up a bit of debris blocking it. Also check for a mixture screw O-ring that has deteriorated for that carb which would make it run lean. Also float/float valve and screen issues which could make a low fuel level in bowl starving that side of engine.

[FM-USA]

Haven't taken the Carbs off yet.

Using my bore-scope I found this 3-way Vacuum T (square box) has one side open to ambient air.
It looks like it's OEM but I simply don't know.
Just odd that a vacuum Tee would be made this way.

1991 GL1500 17163-MN5-000

Internet pix, not mine.

[Rambozo]

It is a stock part..

[FM-USA]

It have to be a stock part, nothing around the engine was changed by me or previous owner & I can find the part in the parts list.

OOPS, I envisioned a '?' on your post.

[Rambozo]

I know, OEM is what I meant. It is a vent tee not a vacuum tee. Everyone is surprised by that part. Just a different way of doing things.

[FM-USA]

Makes one wonder how many were capped or plugged up?
Then again, there's no shielding to keep foreign items, like bugs, out.
OH WELL, it is what it is.