Clunk
From RC Helicopter Wiki
(Redirected from Klunk)
The clunk line is the fuel pick-up tube mounted inside a fuel tank. The loose end of this line is weighted with a clunk so that it always moves to the bottom of the tank, no matter what orientation the tank is in. This helps prevent air being picked up with the fuel and causing the engine to run erratically or even stop during aerobatic maneuvers.