TILLOTSON HU Series Service Manual Download Page 6

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Before disassembling carburetor it is imperative to
flush it clean of sawdust and dirt by pouring gasoline
over it and tools.

1.  Remove pump diaphragm cover screws and
       cover.

2.   Remove pump gasket and pump diaphragm.

3.   Remove filtering screen.

4.  Remove main diaphragm cover screws and
       cover.

5.    Remove main diaphragm and gasket.

6.    Remove fulcrum pin screw, pin, control lever

7.   Remove inlet needle

8.  Remove idle and high speed mixture screws
       and springs.

Commercial carburetor cleaner can be used on all
parts except diaphragms and gaskets.  Before
reassembling, rinse all parts in clean gasoline and
blow off with compressed air.  Do not use cloth, as
tiny particles of lint adhering to carburetor parts will
cause malfunction.  Channels in the metering body
can be cleaned by blowing through idle and high-
speed mixture screw orifices.  Do not use wires or
drills to clean orifices.

and spring.

Be certain both diaphragms are installed
correctly – the pump diaphragm next to the
metering body, then the gasket – the main
diaphragm gasket, then the main diaphragm.
Evenly tighten all screws to insure complete
seal.

When reassembling the inlet control lever and
spring, care should be taken to see that the spring
rests in the well of the metering body and locates on
the dimple of the inlet control lever (as illustrated
above).  CAUTION:  Do not stretch spring.  Inlet
control lever is properly set when flush with the floor
of the diaphragm chamber.   If diaphragm end of
control lever is low, pry up.  If lever is high, depress
diaphragm end and push on needle for proper
adjustment.  (See illustration).  On some models the
inlet control lever is hooked to the inlet needle at
one end.  Special care is required when
reassembling these parts to insure proper operation.

CAUTION:

Under extreme conditions of clogged idle fuel channel
and discharge ports, it may be necessary to remove the
channel welch plug. If so, it must be done very carefully
in the following manner:

1.   Drill a 1/8” diameter hole through the 9/32” diameter
welch plug.  This hole should just break through the
welch plug.  Deeper drilling will seriously damage the
body casting and render the carburetor non-serviceable.

2.   Carefully pry out the welch plug and clean discharge
ports and cross channels.  To re-install, place welch plug
in well, convex side up, and flatten with a flat end tool
slightly larger than the welch plug.

3.  A nozzle brass cup plug can be removed in the same
manner by using a 5/32” drill, or if you have a check ball
cage this should be pressed out and a new one pressed
in.