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PZ26 Carburetor Tuning Guide
Float Height
The oat height controls the fuel level in the oat bowl,
which can also effect carburetor performance. Set oat
height according to specication before any other tuning.
The oat height may need to be adjusted for best perfor-
mance on different track types.
Idle / Low Speed
Tuning of the engine at idle and low speeds is accomplished
by adjusting the Idle Mixture Screw or changing the size of
the Pilot Jet (also called Slow Jet). The jet size or diameter in
millimeters is stamped on the jet (37 = .37mm orice). The
Idle Mixture Screw is a fuel adjustment, so closing the screw
or turning it clockwise will lean the fuel mixture, and opening
the screw or turning it counterclockwise will richen the
fuel mixture.
To adjust the Idle Mixture Screw proceed as follows. Turn
the Idle Mixture screw in until it lightly seats or stops. Back
the screw out the specied number of turns. Warm the
engine and set the Idle Speed screw slightly higher than
the desired idle rpm. Turn the Idle Mixture screw in or out
to obtain the highest rpm. Turn the Idle Speed screw to the
desired idle rpm. A slightly rich idle mixture is usually better
for acceleration.
If a smooth idle cannot be obtained with the Idle Mixture
screw between 1/4 - 2 turns out from closed, a different
size Pilot Jet may be needed. The proper size Pilot Jet will
allow for smooth acceleration from an idle and steady
engine speed up to 1/4 throttle opening.
Midrange / Part Throttle
The Jet Needle primarily controls fuel ow between 1/4
and 3/4 throttle opening. The Jet Needle has ve notches
and a C-clip on the top of it. To richen the part throttle
operation, move the clip to the next lower notch. This will
hold the needle farther out of the nozzle. To lean the
part throttle operation, move the clip to the next higher
position. The highest notch (farthest from the narrow tip)
is considered the 1st position. Needle taper reference
letters are stamped on the needle for identication.
High Speed / Full Throttle
The Main Jet controls the fuel ow at throttle positions of
1/2 to full throttle. The jet size or diameter in millimeters
is stamped on the jet. Altitude and weather conditions can
effect the engine operation enough to require changing
the size of the Main Jet. High air temperature, humidity, or
altitude could require a smaller Main Jet. Low temperature,
humidity, or altitude would require a larger diameter Main
Jet. Running the engine with an improper Main Jet could
result in a loss of power, high engine temperatures, or
engine damage.
PZ Carburetor General Specifications
Gasoline
Main Jet - #102
Pilot Jet - (Slow Jet) #37
Jet Needle - CDB 4th notch
Main Nozzle diameter - 2.6 mm
Idle Mixture Screw turns out - 1-1/2
Float Height* - 14.0mm
Torque Specifications
Bowl Screws 17 – 20 in-lbs.
Pilot Jet 9 – 12 in-lbs.
Needle Jet 14 – 16 in-lbs.
Main Jet 9 – 11 in-lbs.
11
WORLD FORMULA ENGINES
Not for
Reproduction