Carb help, bad idle

My XJ1100 has a rough idle, runs good otherwise. I have been through the carbs twice and cleaned all the fuel passages and jets, main and pilot. Still idles rough. Carbs were soaken in cleaner and blown out with compressed air.
Here's what I have done... all seems OK
-plugs, air filter and air box is clean
-seems to have good spark at the plugs, timing is good
-synced carbs and used home made YICS tool, nothing out of ordinary here
-idle screws are out 1 1/2 turns(this is recomended in the Yamaha manual),tried different settings and still same result.
-float needles and level are in check
-compression test on each cylinder were good(120 psi)
-no vaccum leaks that I can find
Once the enging gets above 1500 rpm it runs smooth
I am at a loss here can anyone make any more suggestions. I'm thinking I may have a bad carb but not sure which one.

 

What's it doing?

Stalling, hunting, Idle-a-bit, ... then, putt-putt-putt and idle some more??

If the carb are synced OK ... and you don't have a Colortune Plug to help set the Pilot Mixtures ... you can "Old School Tweak" them for a steady idle.

Blow-off the Manual and run them screws out to ...
More than 2-3/4 -- Less than 3. Split the difference closer to 3.
Run it.

Go by "Ear"
Micro-tweak 1 Out ... listening to the Idle ... continue out if Idle improves.
Eventually, there will be a "Spot" where there's no further improvement.
You will probably tweak past that spot.
When there is no further improvement; stop.
Do the same for 2, 3 & 4.
Adjust the Idle Rod as needed throughout the process.
Redo all 4.
Tweak IN until the Idle begins to "Stumble"
Micro-tweak OUT until smooth idle returns.
Same for 2, 3 & 4.

Test the bike on the road.
This Old-fashioned method usually is very slightly rich ...
Better to be a little rich ... run cool and save the valves ...
Than ... lean ... which will cause problems across the board.

A Colortune Plug will do this without the guesswork.

 

Have you turned all the mixture screws all the way in then 5 or 6 turns out and had no difference at all to the idle, did not run worse or die?

If so you did not manage to get all the jets clear, when you change the mixture you should hear a change in the motor! (or you have a bad vacuum leak, split in intake boots, damaged butterfly seals? ).

It is better to use a aerosol can of carb cleaner and make sure you can see the cleaner leaving the jet (or jets) at the other end(s). When finished give 'em a good going over with the compressor.

Give them another clean with a aerosol can of carb cleaner and see if that fixes things.

Remove the mixture screws completely when you clean the carbs, be careful not to loose or misplace small parts. Return them to 1 1/2 turns on reasembily. Follow the rest of Rick's post to (but starting at 1 1/2 truns) to tune by ear.

People have trouble cleaning the passage in the float bowl, take special note that this is clear.

Be careful with the mixture screws, bottoming them out hard can damage the point of the jet, the "ears" of the jet can be snapped or sheared as well.

Carb cleaner can damage rubber seals (like on the butterfly shafts) don't soak them.

Other things to try:
Are you sure sync is OK?
Try sync without YICS tool?
Does it run OK on choke? When warm?
Swap coils with the 750?
Any backfire?

Anyway I hope this has been of some help .

 

make sure the "o-ring" at the bottom of the idle mixtue screw is in good shape and is not sticking to the brass screw. That is what was wrong with mine and once Polock replaced them she idled real good.

 

Great suggestions,
I'm going to give another try this weekend. I haven't tried backing out the idle screws 5 or 6 turns. If that doesn't help I'll take the carbs out and check the O rings and butterfly seals, and re-clean the passages in the carbs. It is a good possibility that the seals are ruined from soaking. I'll make anothe post in a week or so and let you know.
Thanks for the input