These guidelines make several assumptions, among which are:
- You own a workshop manual covering the SU HIF-series carburetors. A number of good-quality
manuals dedicated to the SU are available and are highly recommended. It is strongly
recommended that you understand the theory of operation and the mechanical layout of the
carburetor before you start.
- You have installed the intake manifold and carburetor with all correct gaskets and fittings
and have obtained throttle and choke cable of sufficient length to correctly operate the
carburetor.
- You have installed at least two throttle-return springs.
General Information:
The HIF-series carburetor differs from the HF-series primarily in:
- The design and location of the float chamber, which has been incorporated in the body of
the carburetor, and
- The introduction of temperature-sensitive mixture control (a bi-metallic strip fitted to
the jet adjusting screw mechanism) to compensate for varying fuel densities resulting from
changes in fuel temperature.
These procedures cover very generally the connection of both the throttle and choke linkages and
provide a key to correctly dealing with the various tubes and ports of the carb.
Choke and Throttle Cable Setup:
- Route the cables as required for your particular installation and connect them to the
linkage attachment points.
- Adjust both cables to give full range of motion without binding. The gas pedal should open
the throttle fully at the same time it hits the floor. If the pedal travel is stopped by the
throttle reaching the full open position, the result will be stretched and/or broken cables,
bent linkage parts and increases the possibility of a jammed or sticking throttle.
- Make sure that the linkage is free of any bind or interference and that it the return
springs close it completely when released.
- The choke cable requires the same care. Adjust the cable such that it gives the full range
of motion with no binding, taking particular care to see that it completely disengages when the
choke cable is pushed to the fully off position.
Carburetor Hoses and Ports:
Note that all locations are described based on holding the carb in your hand with the suction
chamber upright and the rear of the intake throat (butterfly end) facing away from you.
- Vacuum connection. Located at the rear of the suction chamber, it is a tube about 1/8" in
diameter and has a prominent nipple on the end. If you are not using a vacuum-advance
distributor, cover this tube with some sort of blank tube cover or line cap. If you plug the
tube (or any other tube or hose connection for that matter), make sure you can unplug it should
you require its use in future.
- Float bowl vent. This is a tube about ¼" in diameter located on the right side of
the carb at the base of the suction chamber. Connect this to the air cleaner.
- Fuel inlet. Located directly below the float bowl vent. Connect this to the supply line
from the fuel pump. This line should have a hose clamp around it at the carburetor for safety
reasons.
- Large tube at right base of suction chamber and to the rear of the fuel bowl vent. Cap this
line. You will not be using it.
Initial Settings and Adjustments:
Before starting the engine, ensure that the ignition system is in good condition and that point
and timing settings are correct. Also check and ensure that the carburetor dashpot oil is at
the correct level.
Remove the three securing screws and remove the suction chamber and piston. Looking straight
down through the hole, set the jet needle tube at flush with the bridge and the back it down
½ turn. The mixture adjusting screw is in a tunnel on the right front, directly below
the fuel inlet tube.
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