need help with first bike

I've recently bought a 1982 kz750e and i'm having trouble with the idle.
what it's doing is when it's warmed up it idles high between 4 and 6 thousand RPM.now i'm a little scared of riding it because of that. but at first i thought the needles were sticking, i'm really not sure what it is. but it only does it when it's warm. if any one could help me with this i would be very greatfull.

thank you.

Welcome to the forum.
This is probably a dumb question on my part but have you tried turning the idle down ? The idle adjustment (assuming you have the same carbs as me) is a black knob underneath and slightly behind carbs # 2 and 3.
Idle speed when warm should be about 1200 or 1300rpm.

yah i saw that in my clmyer book unfortuntly that didn't work:(

Check and see if you have any vacuum leaks.

My brothers bike started doing this after he put the carbs back on. It turned out to be just a stupid mistake because when he put the throttle cables back into the carbs he messed up which cable should be turned in more and He got the throttle advance cable to tight and it wouldn't let the thing that opens the butterflies sit down against the throttle adjust screw. If I were you I would disconnect the throttle cables and run it and see if it idles before I went digging in the carbs for something worse.

I'm not sure I fully ubderstand the problem.
Does it start normally using the choke ? and then you shut off the choke (gradually) and then the idle goes to 4,000rpm as it warms ?
If the idle knob does not let you turn down any more then like Becker says check the throttle cable. You should have a little bit of slack in the throttle. You should be able to turn the throttle grip about a 1/4 inch before it starts to pull the cable. If you are not seeing this then check cable adjustment at the handlebars and you may have to take the gas tank off and check the adjustment at the carbs. The cable itself may just be caught up somewhere between throttle grip and carbs.

the bike starts up just fine with the choke and then take if off gradually. then i take it out once it's ready buy when i'm riding around and i come to a stop i pull in the clutch and return the throttle to the closed position. the rpm s spike when i pull in the clutch.

there are even times that i have let go of the throttle completely and the bike has stayed under power, crusing around 30 35 miles per hour

I must say this sounds like a throttle cable issue. You may have to remove the fuel tank to be sure, but make sure your throttle is returning to the stop. It's possible your bike may have a 'push' and a 'pull' cable. Either cable failing can cause the condition you've described. Get a service manual and check it out.

Not sure whether you have CV34 or BS34 but I suspect you have only one throttle cable. It should have VISIBLE SLACK in the cable down near the carburetors. If it has slack, it could be that the venturis have crud built up and the throttle butterflies are unable to close easily. This is pretty common on both the Keihin and Mikuni constant velocity carburetors. A ridge of crud builds up where the throttle butterflies are located. Other things that can cause this are bad choke plunger pads (on the Mikunis), bad carb holders (not sealing), missing or badly cracked vacuum caps on the carb vacuum ports. Missing or very bad mixture screw orings. On the CV34s, if the carburetors have been disassembled, if they were reassembled incorrectly, it can cause binding that will cause the throttle butterflies to hang and the idle to shoot up. Lots of possibilities.