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Specifications subject to change without notice - Check our website for valuable information including videos, workshop and operations manuals. www.jjamusements.com
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ENDURANCE CL
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IDLE (PILOT) CIRCUIT
To provide fuel for idling (when throttle blade is closed) a special circuit feeds just above the main circuit and routes
fuel out of the float bowl, through the pilot jet, mixes it with air from the idle air corrector and circulates it around the
throttle blade to provide a fuel/air mixture so the engine will continue to run when blade is closed. Fuel is pushed out
of the float bowl and up the idle circuit by a pressure differential. The idle air corrector introduces a calibrated amount
of air into the circuit; this air/fuel mixture passes through the adjustable idle mixture screw jet and discharges into the
intake track beyond the throttle blade.
NOTE: The pilot jet is the smallest orifice in the carb. It can be removed and cleaned without removing or
disassembling the carburetor. Remove the idle stop screw and gently pry out the pilot jet assembly (it is held in by an
“O” ring). Make sure the fuel strainer and float bowl are clear of debris before restarting the engine. The pilot jet is a
replaceable part, however, no alternate sizes are available.
With the pilot jet removed, other blockage can be cleaned by removing the idle mixture adjustment screw and using a
fine tipped air nozzle to blow out back through the passages. An aerosol can of carburetor cleaner with a spray tip can
be used to clean and trace out various carb circuits.
TRANSITION CIRCUIT
This part of the idle circuit splits off ahead of the idle mixture screw and feeds a series of very small parts that open just
as the throttle blade begins to move. This provides an extra amount of fuel for a smooth transition from idle circuit to
the main circuit. If the engine hesitates just off the idle on smooth acceleration, you could have fuel restriction in this
area.
MAIN CIRCUIT
From approximately 1/8” of throttle to fully open, the main circuit flows fuel out of the float bowl through the main fuel
jet, up the main air fuel nozzle to the venturi. The fuel delivery carburetor circuits used in this application have two
requirements: fuel and air in calibrated amounts. This provides the air/fuel ratio the engine requires. When cleaning
passageways and/or troubleshooting, it is always necessary to clear the air passage, as well as the fuel passage. The
holes in the side of the nozzle start out small at the bottom and get larger toward the top. These holes introduce air into
the main circuit and also prevent fuel from siphoning into the engine intake.
NOTE: The main circuit controls engine fuel from 1/8” of open to full open. Any carburetor problems below that range
cannot be caused by the main circuit.
CHOKE
A cold engine requires a richer air/fuel ratio to run until the engine combustion chamber temperatures are optimal. To
accomplish this, available air is reduced by “choking” off available air to the engine. A simple flap restricting the bore
does this job.
NOTE: The original Honda/Keihin carburetor uses a plastic composite choke shaft and lever system. This has proven
not to withstand the rigors of concession go-kart use, therefore, J&J builds an all-metal replacement for this system. Part
# 2090017METAL.
THROTTLE BLADE/LEVER SYSTEM
This part is not replaceable, however, throttle plate screws can loosen slightly and cause idling problems with bad
fit in the carb bore. Seat the blade and snug the screws; these screws are “peened” over on the end and are nearly
impossible to remove. Extended shaft wear can cause an air leak around the throttle blade and cause erratic and/or
high idle.
NOTE: Any carb jet can build up with varnish or other material that will not be dislodged with carburetor cleaner or an
air blast. Always hold them up to the light and verify that there is a nice, clean, round hole.
KEEP YOUR K&N AIR FILTERS CLEAN AND OILED WITH ORIGINAL K&N FILTER
CLEANER AND K&N FILTER OIL.
K&N oil/cleaner kit #99-5000C
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