Carburetor Adjustments & Tuning Tips
128 Adjustments for Competition
Carburetor Minor Adjustments
The standard carburetor settings are ideal for the
following conditions: sea level altitude, and 68°F
(20°C ) air temperature. If your conditions are
different, you may need to adjust the carburetor
settings, using the tuning information on pages
126 and 127. Confirm your settings are correct
before proceeding.
Minor
Adjustments
1. Adjust the carburetor setting using the tuning
information on pages 126 and 127.
2. When the engine is warm enough to run
without the choke, push the choke knob down
to its off position.
3. Adjust the pilot screw (1) to obtain the best
off-idle performance.
– If the engine blubbers (rich) exiting a
corner, turn the pilot screw clockwise to
lean the mixture.
– If the engine surges (lean) exiting a corner,
turn the pilot screw counter clockwise to
richen the mixture.
The minimum to maximum range of pilot screw
adjustments is 1 to 3 turns out from the lightly
seated position. If you exceed 3 turns out, the
next smallest slow jet is needed. If you are under
1 turn out, the next larger slow jet is needed.
(1) pilot screw
Adjustment Procedure
1. Warm up the engine.
2. Make 2 – 3 laps of a course with the standard
setting or corrected jetting (page 126). and
spark plug. Note engine acceleration and
other engine conditions in relation to throttle
opening. Verify carburetion by removing the
spark plug and reading its firing end (page
54). It may take more than two or three laps
to get a good spark plug reading with a new
spark plug.
3. Change carburetor settings or select suitable
carburetor jets, taking into consideration the
engine conditions and factors for temperature
and altitude (page 126).
WARNING
Gasoline is highly flammable and
explosive. You can be burned or
seriously injured when handing fuel.
• Stop the engine and keep heat, sparks
and flame away.
• Handle fuel only outdoors.
• Wipe up spills immediately.
4. Turn the fuel valve OFF, and disconnect the
fuel line from the fuel valve.
5. Loosen the connecting and insulator band
screws. Rotate the carburetor. Remove the
float bowl plug (2).
(2) float bowl plug
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