Service manual

FUEL/ CARBURATOR
Fuel Delivery
The throttle opening chart below demonstrates component
relationship to fuel flow versus throttle valve opening.
The pilot system’s main function is that of a low speed jet. Its
most effective range of fuel delivery is from idle to
approximately 3/8 throttle valve opening.
The throttle slide controls the rate of engine air by its
movement up and down in the carburetor venturi. At small
throttle openings the air flow is regulated chiefly by the valve
cutaway, with greatest effectiveness at 1/4 throttle opening.
Throttle valves are numbered 1.0, 1.5, 2.0, etc., according to
the size of the cutaway.
Decreasing the cutaway number will increase the amount of
fuel delivered in its effective range.
The jet needle and needle jet have an effective operating range
from approximately 1/8 to 7/8 throttle opening. The amount of
fuel delivered during this range relies upon the jet needle clip
position, as well as the needle jet size and other specifications.
The main jet affects fuel delivery at 1/4 throttle and
consistently increases to full throttle opening.
VENT SYSTEM
The fuel tank vent supplies atmospheric pressure to the
fuel in the tank. The vent must be free of debris and
restrictions to prevent lean mixture and possible engine
damage. All vent linesmust be properly routed to prevent
damage to the line and to prevent contaminants from
entering the tank.
Protect eyes from contact with cleaner. Take appropriate
safety measures during these procedures. Safety
glasses and chemical resistant gloves are required.
Should you get cleaner in your eyes or if you swallow
cleaner, seek medical attention immediately.
CARBURETOR CLEANING
Carburetor cleaners can be extremely caustic. Extended
periods of soaking can loosen the adhesive sealer on the
passage drill-way plugs. Do not soak rubber or plastic
components (such as the vacuum slide diaphragm,
needle seat screen, or O-Rings in caustic cleaning
solutions. Irreparable damage may occur. Do not use
agitator--type carburetor cleaning equipment. Rubber
parts must be cleaned with mild detergent and hot water
only.
1. Thoroughly clean the carburetor body, jets, and all
passages with carburetor cleaner or electrical contact
cleaner.
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