Hello.
I've seen similar threads on RPMs fluctuating with the clutch being pressed, but I feel this is a unique issue.

My CBR does this odd thing, it won't drop below 4-5,000 rpms occasionally on decel, usually when its warm. When the engine is warm/choke off, It idles at 1k, right where she should be. The carbs were recently cleaned.

Engine was recently swapped (It was cracked when put away back in 99). When I took it out this year (first time out in 15 years), a fresher engine was put in. I don't know if it's a carb issue or the cable is sticking. Any input appreciated.

 

Could be sticky throttle cables or an air leak around the carbs/inlet or air screws set incorrectly.

 

Also betting on sticky cables or a vacuum leak somewhere in the hoses. Might be a good idea to go through all of them carefully.

 

Sticking cable - either throttle or choke. Check for broken strands, sometimes inside the plastic casing. Use a cable luber and you should be good to go........