Idle mixture/etc one rich plug

[Mjpcarbon]

Carbs have been ultrasonic cleaned,rebuilt floats adjusted all with great care......however
Xs1100 bike starts right up and idles well but low end is rough. 3 of the plugs are light tan but #1 is very rich.
Where do I look first ? Idle mixture ? Float ? Aside from 4 vac gauges how does one set idle mixture ?
ill go on to ask is my rich #1 culprit of my rough low end ?
thanks for helping and guiding
mark

[cajun31]

When you state you adjusted with great care? Elaborate on what you did. Sounds like you probably got them clean but what else was done. Be detailed in your explanation. These carbs are very finicky until you get them dialed in. We can give you more detailed responses if we know exactly what you have done. It will be more help to you as well. The responses will be more focused on what your problem actually is rather then repeating what you have already done. One of the first questions will be have you synched the carbs.

[Mjpcarbon]

I removed and cleaned all the jets did my best to make sure all passages were clear.. replaced floats,needle and seats. Checked and adjusted the floats.
I did not sync the carbs mainly because I believe 4 vac gauges are needed to perform this operation.

and if that is the first step guide me to the “how to thread” and I’ll return after that process is completed

[Radioguylogs]

As Cajun said, the sync is important to getting all of the cylinders to run evenly. Did you try to get close with a "bench sync" before installing them? Some folks use a bread tie or a wire to adjust the throttle plates so they are opening evenly. I just look at the idle holes in the venturi and adjust the plates so I see the plates are in the same position relative to the holes. Of course I use the vacuum gauges after I install the carbs, but they are usually pretty close after the bench sync.

How did you adjust the idle mixtures screws? Most of us just turn them in until they are lightly seated, then back them out a certain number of turns. The more careful members use the idle drop method to dial them in exactly.

You also might have the #1 spark plug wire arcing to ground. We know the ignition coil is OK, since #4 cylinder is firing concurrently with #1, and #4 is running fine.

[motoman]

Mjp, your gonna need idealy four vacuum gauges, each with there own vacuum hose to be plugged onto each carbs vacuum port. Screws between 1 and 2 and 3 and 4 are sync screws. adjust those to closely match each others vacuum draw. Now start with whatever mixture screw and back it out a ways. Slowly turn it back in till you hear exhaust change sound at which point stop. Now back that same mixture screw out no more than an 1/8th turn. Do other three mixture screws same procedure. During this process you may have to lower idle speed. now re-sync carbs using vacuum gauges as guide.

[DiverRay]

Did you start with the idle mixture screws all turned out the same, after a bread tie sync? That IS the starting point you need to be at. After that, you DO need to sync the carbs with a meter or 4. If you have one vacuum gauge, buy some "T" fittings and off/on valves so you can switch from carb to carb. One hose off each carb boot to a valve, then "T" together until you have one hose going to the gauge. You can switch from carb to carb and make sure they are close.

[DEEBS11]

All good advice. Especially the sync. Also, check to see that the slide needles fit all the way down in their hole. There is sometimes a white plastic washer that has a tit that fits into a tiny hole at the bottom of the slide. It can fool you and cause a terrible off idle rich condition. It happened to me.

[Mjpcarbon]

Bench Sync done, I went ahead and ordered up a 4x gauge set. I sort of understand how the idle mixture will give me the rough low end but why is #1 soooo rich compared to the other 3. Can the idle mix cause this? If a coil wire were shorting I would expect a miss under load but it is happiest beyond 1/8 throttle.
2,3,4 look like this

[DiverRay]

You may have a fuel leak past the needle and seat. I usually "bench test" the carbs by putting them on a 2X4 bracket(takes a couple to build it) that holds them up, and hooking my small sync fuel tank to them. Look as you lift the tank to see if there is a leak, and leave the tank up for two or three minutes to verify none of the carbs are leaking.

[Larrym]

replaced floats,needle and seats. Checked and adjusted the floats.


Iffin' they came from Ebay in boxes like these?


Then setting the float height to the "recommended" distance per the repair manual is NOT gonna wurky. ﾍ(￣ー￣)ﾉ

Too much difference in the Taiwan parts compared to the OEM and variance between each float/needle/seat themselves.

BTDT. (◕__◕)



As far as needing to Sync the carbs? (O_o)7

ThreePhase rode his XS1100 all the way from Cali to the US/Canadian border with just a bench sync. We took a few rides together and made a video showing how well the bike ran. THEN when I drove down to Cali months later?

That's when we hooked up my sync gauges and made a video of him doing it. (O_O)

My take-a-way? Good bench sync and everything else working right is good enuf until you can ride to someone who does got the gauges. (^_^)

[cajun31]

What year/model bike do you have? Do you know if the carbs are original to the bike?

[Mjpcarbon]

Carbs are original
79 non special

[DiverRay]

Check the float in #1. Pull the float and shake it. If you can hear something inside, it has a leak.
Check float bowel gaskets for clearance. Some will intrude into the bowel and cause the float to hang up and not work correctly.
Verify the needle and seats are Mikuni. I've had problems with K&L seats on some bikes, and others are junk.
Check spring length on all 4 carbs for the vacuum control of the needles. These are the large springs that keep the needle down until engine vacuum goes up, the CV part of the carbs.
Make SURE the clip is in the same position on all 4 needles.

[Larrym]

I've had problems with K&L seats on some bikes, and others are junk.

With the kits (needle/seat/jets) shown ALL were near flooding the bowl over and #3 carb WAS flooding up/over/into the engine and airbox. (⇀‸↼‶)

This was even though the float height was "SET" to the right height per the repair manual. (－‸ ლ)

#3 plug was BLACK around the outer ring (like your #1) but the electrode/anode was clean as a whistle cuz the unburned gas was washing it that-a-way as gas is also an excellent solvent. (Θ︹Θ)

I replaced #3 and #4 needle/seats (#4 had the wimpiest spring I'd ever seen and not nearly the same as the other three...) with K&L. (≖ ︿ ≖ )

I mean K&L is from Japan like the Bike so's I though they'd wurky, right? ┐(´～｀)┌

NOPE.... (つ﹏<。)

Even the K&L needles/seats didn't get the right fuel level in the bowl(s) when set to the recommended float height. (╯°□°）╯

To get my super bike back to being super? ( 　ﾟ ,_ゝﾟ)

Had to build the "Carb Pagoda", set up fOaR seeing the real/actual fuel level in each bowl, and adjust/measure till all were right. (　`_ゝ´)

But then I REALLY like having a super bike that runs like a super bike. (*＾▽＾)／

[Mjpcarbon]

Update and more guidance needed. I hooked up the 4 vac gauges and with the gauges fully open the needles are wild. If I dial down the gauges the needle gets steady but still moving slightly.
Idle mix screws really dont seem to have much effect on the gauges.

Symptom, after much tinkering I no longer have a subtle miss however the idle is infuriating, if I rev it, the idle drops to 2000 then will slowly drop down to a very rough 1000. If I increase the idle screw just a touch it pretty much stays at 2000.
I am a bit lost. I rebuild vintage marine engines for a living but this is kicking my ass.