Erratic/high idle

I`ve had this problem since I got the bike and it seems to come and go,worse when it`s hot.Engine idles fine at start up but after running a while will not idle down when I let off the throttle and will stay around 2-3k untill I release the clutch a little and it will drop back down to 1k.I know it is carb related as a borrowed set of carbs worked fine.I have been thru the carbs cleaning and adjusting them to no avail,what could be causing this?Bike has the stock 42mm carbs back on it with Emgo pods,needle raised one position and rejetted for the pods,pulls fine thru rpm range but possibly a little lean and I may need to go up one more step n the jetting,otherwise bike is stock.

Have you checked the choke plungers? I had erratic idle problems on my KZ900 and finally checked out the plungers next to each carb. The ones on the right were completely visible and were closed when the choke was closed. The ones on the left were harder to see. They were not closed. A seemingly easy adjustment and a little oil on the shafts and she idled beautifully!

What kind of adjustment?Mine seem to open and close fine with the choke lever,seems to be pretty foolproof mechanism.Any other ideas?

The choke plungers may not close all the way because of binding or the plunger not sliding cleanly through the rubber cap. If they are real dirty, they don't slide easily and the choke could be left slightly open. This WILL cause the problem you describe. The binding issue can be resolved by removing the carbs from the bike. Take off the screw on the end of the lever that is used to hold the lever. You should be able to pull the choke lever up and it should go down easily all by itself. If there is binding, you can loosen the four set screws that hold the choke actuator arms on the choke rod and slightly reposition the arms.

Another reason for erratic idle is that the pads on the plungers are hardened or deteriorated. Remove the choke plungers and examine the pads. If there is a deep indentation or they are deteriorated, they need to be replaced... the rubber pad seals the enrichener circuit and if they don't seal well, erratic idle will occur.

Next step is seal on pilot mixture screws. The orings must be in good shape and the proper size or air leaks into the pilot system....

You can also get air leaks in other locations; carb holders or caps on sync ports on the carb holders. This can be checked with the engine running by spraying with WD40. You will get white smoke or the engine will die if you have a leak. Replace what is leaking.

Last is fairly rare for the return spring for the bellcrank may be tired or the wrong spring. I have seen this happen a number of times... the spring is just not up to keeping the slides closed securely. This generally happens after a shop works on a set of carbs and installs the spring from a 650 VM24 on a VM26 or larger carb which has a slightly stouter spring (larger gauge metal).

I rechecked for vacuum leaks but found none.I did some more fine tuning with the floats and mixture screws and it seemed much better but I need to take it out again for a longer ride to make sure it is fixed.