DESCRIPTION
All carbureted models are equipped with a thermostatic air cleaner. It is equipped with an air control valve inside the snorkel which allows either heated exhaust shroud air or cooler ambient air into the carburetor, depending on valve position. A vacuum motor which responds to a bimetal sensor (part of thermosensor) controls valve position.
OPERATION
When incoming air temperature is below predetermined temperature, air control valve will be in up (hot air only) position. When temperature has reached a predetermined temperature, valve will be in down (cold air only) position. At in-between temperatures, control valve is positioned to blend both hot and cold air. When system operates properly, air temperature is kept constant.
| Valve Up: °F (°C) | Valve Down: °F (°C) |
|---|---|
| 86 (30) | 113 (45) |
AIR CONTROL VALVE TEMPERATURE SETTINGS
SYSTEM
- Make sure all vacuum hoses and heat cowl to air cleaner air duct are properly attached and in good condition. With engine cold and ambient temperature less than 86°F (30°C), the air control valve should be in up (hot air only) position.
- With engine at normal operating temperature, check air temperature entering outer end of snorkel. When air entering snorkel is 113°F (45°C) or higher, valve should be in down (cold air only) position.
AIR CONTROL VALVE
Remove air cleaner. Disconnect vacuum hose from air control valve and connect a vacuum pump to nipple. Apply 19.8 in. Hg of vacuum. Vacuum should hold. At 2.6 in. Hg of vacuum or less, valve should be in down (cold air only) position. At 7.4 in. Hg of vacuum or more, valve should be in up (hot air only) position.
THERMOSENSOR
Connect vacuum pump to thermosensor nipple and apply vacuum. At 86°F (30°C) or less, vacuum should hold. At 113°F (45°C) or more, vacuum should leak.
