Carburetor Mixture Adjustment - Johnson J10RSUR Service Manual

FUEL SYSTEM

CARBURETOR MIXTURE ADJUSTMENT

CARBURETOR MIXTURE
ADJUSTMENT
IMPORTANT:
Changing original factory fuel
mixture calibrations beyond the limits allowed by
the tamper resistant device is a violation of federal
law. Any needle valve adjustments beyond preset
limits become the responsibility of the servicing
technician and/or the owner. Refer to Emissions
Compliance on p. 107.
If the carburetor body cover assembly must be
replaced; or, if the original calibration settings are
lost, the following procedure can be used to make
adjustments based on engine performance.
Adjustment of the tamper resistant needle valve
requires a special Torx Screwdriver, P/N 351204.
Start the engine and run it in FORWARD at one-
half throttle. Allow the engine to reach normal
operating temperature.
Tiller Models
Face the steering handle. Turn the idle speed
adjustment knob counterclockwise to lowest
SLOW speed position.
Run the engine at slow speed (700 to 800 RPM)
and adjust the low-speed needle until the highest
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consistent RPM is attained. Allow 15 seconds
after each adjustment for the engine to respond.
1. Low-speed needle
Reduce engine speed and turn the idle speed
adjustment to allow the engine to run at a mini-
mum of 650 RPM in FORWARD.
Run the engine in gear near full throttle for one
minute. Quickly reduce speed to SLOW (700 to
800 RPM) and shift into NEUTRAL. The engine
should continue to run smoothly.
If the engine stalls or pops, the mixture is too lean.
Turn the needle counterclockwise 1/16 turn. Allow
15 seconds after each adjustment for the engine
to respond. Do the previous step again to make
sure the mixture adjustment is correct.
If the engine does not respond to adjustments,
check it for other problems. Make sure gasoline is
of good quality and mixed with the proper amount
of oil.
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35008