Revs slow to drop.

I am trying out a spare set of carburettors on my bike. Stripped and cleaned all the jets, it seems to be running ok but when I rev it and then close the throttle, the revs are slow to drop back down to tick over. I have checked the carb rubbers are properly tightened to stop any air leaks and they seem ok.
Any helpful suggestions would be greatly appreciated.

McZed - presumably you've ensured a slight amount of slack in the throttle cable.

Check your fast idle/choke adjustment. (Choke cam and roller) The manual is very specific about this adjustment. If it is not adjusted correctly the small roller will ride on the fast idle/choke cam and not on the idle stop which is adjusted separately by the long adjusting screw between the left and center carbs. Details on page 50 of the manual.