TOPIC:

I've got the new engine in the bike and looks like I have most of my issues sorted except the carbs.

My idle is much too high.. around 2500 rpm and doesn't go any lower no matter how far I back the idle adjustment screw. It spins but nothing changes... I can speed it up but not slow it down.

When I crack the throttle the rpms drop to normal very slowly and sometimes it continues to race higher until I hit the kill switch.

It is probably something simple but I don't know much about carbs. One could argue I don't know much about bikes in general but I'm learning fast.

It isn't back firing, missing or otherwise acting weird.

It sounds like you need to turn the balance adjusting screws down a bit. These are on the three rods that actuate the butterfly valves on your carbs. You cant miss them, one on each carb small hex head with a locknut, sticking up just above the carb tops. slacken off the lock nut and screw them down a little, do this with vacuum gauges attached if you have them. If not you will have to do it by ear.

I take it you haven't altered the carbs. Before anything I would ensure that your Throttle cables have been set up correctly.

This set up really is a fine art. There is a co-relationship between the 3 carb link rods, the idle set screw and the fast idle set screw. I'm not sure if Scotch covered the set up in his carb rebuilding article under the Build Blog Tab. I know I spent literally hours playing with the 3 adjustments until I finally got what I wanted. After I finally got it right, I thought it would be prudent to write up a instruction regarding the initial adjustment. I just didn't get around to it as of yet.

One of the other considerations is that you're trying to idle the motor on the main circuit. It's possible to have the idle circuit not working and the motor trying to idle down on the main. Problem is there's enough vacuum in the venturi to cause the throttle sleeves to be slightly off there home position, feeding fuel to the engine. If that's the case, then a slow drop to a high idle could be expected.

I hung the tank between two ladders and started messing with those screws. It is a much better than it was. My idle is smooth at 1000 or so rpm and it drops off as it should when I cut the throttle. The carbs should still be cleaned and balanced by a pro but this is good enough to give it a test run if it ever stops raining.

I've discovered another small problem. I don't think my temperature gauge is working. The previous owner had a fan switch rigged so I prudently left the fan running while I played with the carbs. I didn't see the temp gauge move at all so I must be missing a connection somewhere. It makes it harder to trace down wiring problems when the previous owner(s) butchered the wiring.

At least it runs!

"<.........and started messing with those screws.>

What you likely did by "messing" with those screws is loosen them enough to reduce the friction (drag) they were creating by being wound in too tight to begin with. When turned in too far even all the return-springs have a difficult time getting the throttle-plates closed (if they'll close at all) That's the first part of your issue dealt with. Now it sounds like you need to adjust the fast-idle cam/roller setting. See the manual for the specs. From there you can it adjust slightly to suit your engines specific idiosyncrasies.
The choke/fast-idle adjustment can can be finicky so you may need to "play" with it over the course of several days so you know you have a good setting when you start cold. I personally like a "little" throttle-plate opening BEFORE the plungers lift.