CBR1000 - clean carbs, lousy idle problem

Bike is a 1990 with 8,000 original miles, and is extremely clean and well
kept for its age (the point is that I know that I'm not chasing gremlins
such as a rusty tank, corroded connectors, etc).

Bike starts okay... idles rough. When I twist the throttle slowly, it will
climb up to 2000 rpm roughly but successfully. It runs fine over 2000 rpm.
When I blip the throttle quickly, it coughs terribly, and seems like its
misfiring terribly... and if I don't let up on the throttle, it dies.

I've removed and cleaned the carbs three times. They look almost new.
Every passage got elbow grease in conjunction with carb cleaner and a blast
of compressed air. I took off the jets, the floats, the diaphrams,
everything. There wasn't a speck of gunk in there anywhere, and everything
moves smoothly. The pilot screws are also A-OK.

I checked the fuel filter in the tank - its like new.

Plugs all look normal - none fouled, none wet with oil or gas, they look
ideal.

I took it to two shops: they didn't bother looking at the bike - but both
insisted that all I need to do is clean the carbs.

The damn carbs are clean.

Help?!

 

On the off chance that Do you have clean carbs you might have an intake
valve not seating completely causing your problems If the bike has sat for a
while or seen limited use it may have rusted or gummed up valve stems or
face/seat.
Hook up a timing light to each cyl one at a time and look down each carb
throat at idle to see if there is and fuel being spit back.
But I wouldn't rule out dirty carbs

 

I fully agree.When I balanced my brothers' CBR1000 carbs I could stop the engine with a tiny
adjustment on the balancing screws.