Allis-Chalmers WD Operating Instructions And Repair Parts Illustrations page 17

CARBURETOR - The Zenith Model 161 Series
has three adjustments, one for controlling the
idling speed of the engine and two for correct-
ing changes in fuel and atmospheric condi-
t i o n s . To regulate idling speed of the engine
adjust the throttle stop screw on inner side
of the carburetor. For correct fuel mixture
at idling speeds of engine adjust needle valve
on front top of the carburetor. Turn needle
in for richer mixture. Normal setting is
approximately one and one-half turns out.
The main jet adjusting needle located on the
lower front of the carburetor body regulates
the fuel mixture at working speeds. Turn this
needle out for richer mixture. Normal setting
is two or three turns out depending on fuel
and atmospheric conditions. Always make
carburetor adjustment at normal operating
temperature.
The adjustments of the Marvel Schebler
Carburetor Model TS159 are the same as the
Zenith, except for the main jet adjusting
needle located on the front upper portion of
bowl. The normal operating adjustment is
approximately one and three eighths turns out.
Correct clearance between valve stems and
rocker arms should be maintained at all times.
To adjust clearance, turn engine with crank until
valvecloses and push rod is at its lowest posi-
t i o n .
Loosen valve adjusting screw lock nut and turn
screw until there is .010" clearance between
valve stem and rocker arm. Tighten lock nut
and recheck. The engine must be heated to its
normal operating temperature when making this
adjustment.
Lack of compression because of leaky valves
may be caused by either insufficient clearance
between rocker arms and valve stems or by the
collection of carbon on the valve stems or seats.
The engine speed is adjustable by throttle only.
The governor, of the variable speed type, will
control the engine speed within the range of low
idle and 1725 r.p.m.
-MARVEL SCHEBLER CARBURETOR -
VALVE TAPPET C L E A R A N C E
GOVERNOR
To ensure good governor action it is important to
have all linkage from governor to carburetor,
work freely.
17
ZENITH CARBURETOR
ADJUSTING NEEDLE
IDLING ADJUS
IDLING SPEED
CHOKE LEVER
S C R E W
AND LOCKNUT
FEELER GAUGE