Each time a KZ10 cylinder needs to be removed, obviously the coolant needs to be drained out from cooling system.
Leaving a certain amount of fluid in the cooling jacket of the barrel. Even blowing into the radiator leaves some residue coolant in the system.
Is there an easy foolproof method to prevent the small amount of coolant in the water jacket dropping into the crank case when the barrel is removed?
Exactly that will solve the problem. Also, if you are leaving the engine bolted onto the chassis and only removing the cylinder, after you undo the pipe, you can tip the kart up on the engine side so it will drain every last drop