In order to keep the temperature of the air drawn into the carburetor as constant as possible, all engines are equipped with a Hot Air Intake (HAI) System.
In all engines, the system depends on a thermo valve to control the temperature.
At normal temperatures the air is drawn into the inlet in the air filter. When the temperature drops, the valve switches position, opening the way for air to be drawn from around the exhaust manifold.
When inspecting, check all hoses for poor connections or damage and visually check the air control valve in the air duct.
When checking valve movement, do not push too strongly on the control face.
Should there be a malfunction, replace the part involved.