Specifications

27
Mixture Adjustment Procedure
for Adjustable Carburetors
Once the speed control bracket is adjusted, the main
and idle fuel mixtures can be adjusted. Start the engine
and allow it to warm up to normal operating temperature
(3 - 5 minutes). Set the speed control to the HIGH or
FAST position, then turn the main mixture adjustment
screw in (clockwise) slowly until the engine begins to
run erratic (lean). Note the position of the screw. Now,
turn the screw out (counterclockwise) until the engine
begins to run erratic (rich). Turn the screw in (clockwise)
midway between these two positions. This will be the
best setting.
Set the speed control to the IDLE or SLOW position.
Adjust the idle mixture screw following the same
procedure used to adjust the main mixture adjustment.
NOTE
Some carburetors have fixed main jets. The absence
of the adjusting screw indicates a fixed jet and no
adjustment is necessary (diag. 25).
After adjusting the fuel mixtures, engine speeds can
be adjusted. The correct operating speeds are found
on Microfiche card 30 of the Tecumseh Master Parts
Manual, or the computer parts look-up program (Parts
Manager Pro). On engines with adjustable carburetors
(diag. 26 and 27) the high speed adjustment will be in
one of two places. The first location is on the speed
control lever (diag. 26).
The second is on a bracket located between the blower
housing and the speed control (diag. 27). Low speed
is adjusted by the throttle crack screw on the carburetor
(diag. 26 and 27).
The high speed adjustment screw is located on the
speed control lever (diag. 28) Some carburetors are
fixed speed and are adjusted by bending the adjusting
tab attached to the intake manifold (diag. 30).
After setting the engine speeds recheck the fuel
mixtures, then recheck the engine speeds.
HIGH SPEED
ADJUSTMENT
SCREW
LOW SPEED
ADJUSTMENT SCREW
IDLE
MIXTURE
SCREW
MAIN MIXTURE SCREW
COUNTERCLOCKWISE
TO INCREASE SPEED
CLOCKWISE TO
DECREASE SPEED
27


MAIN MIXTURE
SCREW
LOW SPEED
ADJUSTMENT SCREW
IDLE MIXTURE SCREW
HIGH SPEED
ADJUSTMENT SCREW
26
TYPICAL NON ADJUSTABLE CARBURETOR
25
CAPPED JET
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