82’ KZ750E won’t idle down

Alright so I’m pretty new to the forum so looking for a bit of help. I’ve got a 1982 KZ750E the four cylinder. The bike is having a problem coming down from high revs. I’ve recently installed a dynatek DS2 ignition system, coils and wires as well. The bike wasn’t treated well when I got it so I also got a carb rebuild kit as well, and adjusted the mixture screws out 2 turns out them. I’ve now got the bike back together and running, kind of. I can adjust the idle up to a good idle (I’m not sure exactly what the idle is since the tach cable is shot) but when I twist the throttle, the bikes revs shoot up and hang on for a good long while until they come back down. I’ve been battling this issue for a few weeks now and I just can’t find the solution. The bike didn’t run before this because the fella before me didn’t replace the pickup cover gasket and it became rust mania in there, hence why I bought the dynatek. Anyways hoping someone out has found the solution to this, I want to get a good ride in before winter

There are several,possibilities.
The low speed circuits are still clogged up. Unless you completely disassembled each carburetor, unganged the bodies, and made absolutely certain that every tiny passageway in each carb is completely clear, the carbs may try to idle on the main jets, giving you all sorts of headaches.

One or more of the diaphragms may be torn or have tiny holes in them, preventing the slides from working properly.

The throttle cables may be frayed or rusted, or the throttle shaft may be bent or dirty.

If your ignition system has a mechanical advancer, it could still be rusty or dirty enough to not work smoothly.

Adding to TexasKZ's list...

A hanging idle is often caused by lean mixture. On old bikes like ours I recommend replacing the intake boots that bolt to the head because they often leak due to cracking. The airbox boots need to be properly sealed too or the bike won't run right. And needless to say, if you ditched the airbox the carbs will need complete rejetting.

Thank you guys for the tips so far! Took the carbs back off to do another clean to make sure the passages weren’t clogged up, so then I went ahead and tested the carb boots after seeing what you said, got the bike to idle and warm up then set the idle up again so it would stay running, then sprayed carb cleaner on the engine side of the boots and the engine almost stalled immediately, then I did it to the other three and it did the same thing, and actually died one time. So I’ve got new boots on the way, I’ll give an update when I get them on the bike!