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Jetting Your CDK II Diaphragm Carburetors
1) IDLE
Set the idle speed to proper r.p.m. by adjusting
the IDLE SPEED SCREW. Next, turn the IDLE
MIXTURE SCREW to get the highest speed,
then turn out the IDLE MIXTURE SCREW
approximately 1/4 to achieve best response.
The IDLE MIXTURE SCREW controls fuel
delivery to the idle port and also contributes
fuel to the SLOW CIRCUIT.
2) OFF IDLE TO 1/4 THROTTLE
The SLOW JET is the most effective in this
range. WHen you want a richer mixture in the
range, use a larger SLOW JET. The opposite
holds true for achieving a leaner mixture.
3) POP-OFF PRESSURE
In most applications it will not be necessary to
change the POP-OFF PRESSURE. If the engine
is modiied or a larger carburetor is used,
changing POP-OFF to a lower pressure may
beneit the calibration. If engine exhibits poor
acceleration or is lean at W.O.T., try lowering
the POP-OFF pressure by using a lighter
spring or a larger valve.
4) WIDE OPEN THROTTLE
Changing the MAIN JET or HIGH SPEED
SCREW adjustment affects this range. Start
adjusting by turning the HIGH SPEED
SCREW until the best performance is
achieved. Then, check number of turns on
the screw. If the screw is adjusted all the way
in, install a smaller MAIN JET. If the screw is
out more than three turns, install a larger
MAIN JET. Continue until optimum
performance is achieved and the HIGH
SPEED SCREW is at approximately 1 to 1 1/2
turns. This will allow some adjustment range
on the HIGH SPEED SCREW to perform
minor adjustments or to compensate for
temperature changes.
Calibration Chart
(for CDK II)
Internal View
NOTE: Make only one
change at a time.
CDK II Diaphragm Carburetors
532
Main Jet
Slow Jet
Fuel Inlet Seat
Needle Valve
Arm
Regulator Spring
Fuel Chamber
Regulator Diaphragm
High Speed Screw
Atmospheric Vent
Idle Mixture Screw
Idle Port
Throttle Plate
Fuel Inlet
Pulse
Pump
Diaphragm
Check Valves
Fuel Return
Restrictor
Vapor Seperator Anti-Siphon Valve
Transfer
Holes
Water
Idle
1/4
1/2 3/4 W.O.T
Throttle Opening
Effectiveness
High Speed Screw
Main Jet
Slow Jet
I.M.S.