Bench sync for TK carb - need some help

After pulling the TK carbs from my KZ550 to bench sync them, I noticed that the slides for #1 and #2, don't go down as far as the ones do for #3 and #4. This is with the top adjustment screw all the way in for all 4 carbs and no stop screw or idle adjustment screws are impeeding the full throw. The lowest I can get the slide for #1 and #2 is a 4mm opening and I'm wondering if this is too high. I had problems getting the bike to idle below 2000 rpm before I pulled them and I'm wondering if this could be the reason. I could actually get it to idle below 2000 by leaning out the air screws but it would get too lean and have no power from 0-1/4 throttle. I've attached a picture to show the lowest I can get the slide. Just wondering if this is normal or I have a mechanical problem. Also, how big of an opening should I shoot for on the bench sync for the TK carbs?

You don't bench sync from the intake side. You bench sync from the engine side. Back the idle screw all the way out. Loosen the locknuts on the sync screws. Make sure the bellcrank isn't hard up against the cable holder in the center of the rack. If it is, bend the cable holder bracket a tad so it doesn't touch the bell crank. Try turning the sync screws in as far as they will go. If you still have the slides up too high so you can't get the idle within an appropriate range, you indeed have a mechanical issue. At this point, I would totally disassembly and remove the sync mechanism stuff... there will be some little stopper parts and springs. Stretch the springs. With the main jet holder tube out, see if the slides seat down into the venturi. Sometimes there is a burr that keeps them from seating. The main jet holder tube can also be bent from overtightening and the slide would sit down all the way. If you do these things and the slides still won't seat, the slide shaft was drilled inaccurately and you will likely need to replace it... we find that this occurs now and again and it is hard to believe that the old carburetors could be used so long and never be close to right...

Thank you Wiredgeorge! This is very helpful. I need to do some more inspecting but my money's on it being drilled wrong. There is a gap on the engine side for #1 and #2 and I'm not sure what starting position I should be shooting for there when bench sync'ing. Should they be closed or is there a recommended height to start?

Bench sync is misunderstood. Most people believe it is a poor man's way to sync carbs based on references in various shop manuals. Some shop manuals actually explain its true purpose and you have pretty much discovered the reason based on your issues. Don't rule out that the small springs in the sync mechanisms are smooshed and have lost their compression. If you take them out and stretch them, you can add back in some ability to close. The other stuff I mentioned are also real possibilities for the carbs not closing. I have seen it all so don't make an assumption at this point. You can also put an M4 nut down under the top spring and little piece that sits below the spring to hold the sync mechanism down. This can space it slide down about 1 to 2mm IF the mechanism is just tired. Lots of tricks involved with this stuff and since we see about 300-400 sets of carbs a year through the shop, we see this stuff fairly regularly. It is a pain in the butt and takes time to sort.

If it helps at all, my TK22's havn't been disturbed since they came off my 500. See Below,if you want any more photos just say.

Thanks guys for the tips and the picture there. I was able to work a little bit during my lunch hr and I resolved the issues I had with some more adjustments. I'll be putting them back on the bike tonight and will let you know how it works! I got an inexpensive manometer from Z1 and hope to try it out here soon.

Got everything back on the bike...I'm getting faster at taking the carbs on and off now. Basically I raised the 2 lower carbs to the height of the other 2 and they all 4 went down together. Was a "duh" moment. I'm now able to use my idle screw to fine tune the idle also. Whoever had these carbs before had them all out of whack.

The bike runs better than it ever did now. Idle is at 1200 now and runs smoother all the way to wide open. It's going to be in the mid-60's here in Georgia this weekend so I can't wait to go for a longer ride.

Thanks again for your help everyone. I've learned a lot from fixing this little 550 and I can't wait for next winter's project!