The Primer Function

• The carburetor contains three areas: measuring, mixing and pumping stations. These systems work through the pulsing of the crankshaft when the engine is running. For the measuring and mixing to work when the engine is cold, a primer bulb is installed to help them. A primer bulb sucks gas from the tank, up into the fuel hoses and into the carburetor. This brings an adequate supply of fuel into the carburetor when the piston and crankshaft aren't spinning.
  
  

The Primer's Operation

• The primer brings fuel into a cold carburetor through the same vacuum pressure used in the crankshaft's pulsing. When the rubber bulb gets depressed, air is pushed out of the fuel lines; when the primer bulb gets released, fuel gets sucked back into the lines. This operation removes the air from the fuel hoses and brings fuel into the carburetor. Without this added pressure, the carburetor wouldn't receive enough fuel at the beginning to reach the cylinder.
  
  

Primer Setup

• The entire fuel system works in a closed loop. The fuel starts at the tank, and gets pushed up through suction hose before reaching the carburetor. After the carburetor mixes it with air, it sends most of the fuel off to the cylinder for ignition. Any excess fuel left in the carburetor is purged back into the tank via a return hose. The primer bulb is connected to this return hose about midway. This allows the primer bulb to pull gas all the way through the circuit when the engine is cold.
  
  

Primer Problems

• Problems with the primer function on the Featherlite mainly relate to suction problems. Whenever the suction pressure doesn't stay consistent, the primer bulb stops pulling sufficient gas through the system and into the carburetor. Suction problems often result from air leaking somewhere into the fuel system. Air leaks generally occur at the fuel hose connecting points with the tank and the carburetor. Air can also leak into a cracked or loose primer bulb connection.