Speedy Pete Kart Parts

PZ Carburetor Tuning Guide

Idle / Low Speed
Tuning of the engine at idle and low speeds is accomplished by adjusting the idle mixture screw (555585) or changing the size of the pilot jet, also called slow jet. The jet size or diameter in millimeters is stamped on the jet (32 = .32mm orifice). The idle mixture screw is an air bleed adjustment, so closing the screw or turning it clockwise will richen the fuel mixture, and opening the screw or turning it counterclockwise will lean 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 specified 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 1/4 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 / throttle opening.

Mechanica Idle SPEED Adjustments
The overall idle speed is set using the Idle speed screw (555586). Movement of this screw clockwise will raise the slide, effectively raising idle speed. Counterclockwise movement of the screw will lower idle speed. This adjustment will affect the overall idle speed of the engine and with adjustments of the mixing screw, will control idle and initial responsiveness/acceleration of the engine.

Midrange / Part Throttle
The jet needle (555602) primarily controls fuel flow between 1/4 and 3/4 throttle opening. The jet needle has five notches and a C-clip on the top of it. To richen the part throttle operation, move the clip to the next lower notch. To lean the part throttle operation, move the clip to the next higher position. The highest notch (farthest from the tip) is considered the first position. Needle taper reference letters are stamped on the needle for identification.

High Speed / Full Throttle
The main jet (contained in kit 555536 and 555537) controls the fuel.

PZ Carburetor General Specifications

* To check float height

• Remove float bowl and hold carburetor upside down
• Allow float to rest on the inlet needle
• Measure from the fuel bowl mating surface to the bottom edge of the float
• Bend tab were it makes contact with the inlet needle as needed to obtain the correct float height flow 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 size could result in a loss of power or engine damage.

Torque Specifications

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Carburetor Pump Requirements

In our testing we used the Walbro WIP-28 fuel pump, this pump is designed to deliver 1-2 psi pressure at the carburetor on the Animal engine. It also has two longer thru bolts for mounting.

The Walbro PZ Carburetor should not be used with a fuel pump rated at or higher than 5 psi, flooding could occur.