Gs500f getting stuck at rpms

[Skryant-the tyrant]

I recently picked up 2 2005 gs500f, one a naked and one with a cowling... one of the bikes has a problem where when it warms up it will get stuck at 3k rpm. When I originally start the bike cold it revs fine but once warm it drops back down slowly but like I said the warmer it gets the slower the rpm's drop until it gets stuck...

It's NOT the idle screw because I've adjusted that every which way. The problem only occurs when the bike gets warmer.

I've taken apart the carb, cleaned it, the jets are super clean and the seals to the engine to the carb seem fine, and from the carb to the airbox are good as well. Any ideas would be greatly appreciated!

[Armandorf]

An air leak, maybe too lean, how is the mixture screw?