Service Manual

3-5
Table of Contents
Two Barrel Carb./Fuel
Twin Cylinder Engine Service Manual
February 2017 - Digital Edition
TWO BARREL CARBURETOR AND FUEL SYSTEM
Two-Barrel Carburetor
Introduction: The two-barrel carburetor has the advantage of a unique fuel-air mix for each cylinder. Each
barrel has a main jet, nozzle and pilot jet to maximize each cylinder’s output. The two-barrel carburetor is located
between the intake manifold and the air lter manifold. All components are made of aluminum for durability (Figure
4).
Operation
Slow Throttle: To operate in slow throttle operation; throttle is closed (or almost closed), engine is under light load.
Air is drawn through each barrel creating low pressure at the throttle disc. Air at atmospheric pressure in the oat
bowl pushes on the fuel, the fuel is metered through the idle circuit. Fuel ows through the main jets and nozzles
into the idle circuit, air mixes with the fuel at each pilot jet. Fuel-air mix ows through a series of holes on the side
of the barrel near the closed throttle disc. As throttle disc opens with increasing load, more holes are exposed to
low pressure allowing more fuel-air mix into the air stream.
NOTE: Fuel does not ow into the main venturi until the throttle disc opens beyond the holes in the
barrel.
Figure 4