1. Carburetion Fuel Delivery

2. Purpose: produce mixture of fuel & air to operate an engine

3. Basics: 1. Air enters top of carburetor 2. Mixes with liquid fuel 3. Goes through passages 4. Sprayed into intake manifold 5. Burned in combustion chamber

4. Operates based on different pressures Cylinder has no atmospheric pressure Air/fuel mixture is pushed into cylinder by atmospheric pressure in the carb

5. Venturi principle- Restriction in a passage creates a vacume. ( Causes air to move more rapidly)

6. Carbs come in many styles & types Natural draft- air flows horizontally into manifold Updraft- a/f mixtures forced upward toward engine Downdraft- gravity assists air into manifold

7. Float type carburetors Float= maintains constant level of fuel in float bowl When fuel is used float unseats needle valve and allows fuel to enter the bowl

8. Choke- Round disk mounted on shaft at the intake end of the carb. Closed= provides more fuel to the engine to allow starting

9. Adjusting needle- adjusts the amount of fuel entering the nozzle to be discharged. Sometimes these are pre-set & non adjustable

10. Primer- hand operated plunger Forces additional fuel through main nozzle. Mainly used to start cold engines

11. Governor ◦Maintain a selected speed ◦Prevent over-speeding that could cause engine damage ◦Limit high & slow speeds

12. Air Cleaners Engines must have clean air! Dust/moisture ruin engines

13. Servicing an Air Cleaner Change ever 25 hours on lawnmowers Follow manufacturers instructions