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4) 1/4 TO 3/4 THROTTLE
The JET NEEDLE is the most effective
component in the range. Changing the
STRAIGHT DIAMETER (D) will change the
calibration in the transition range from the
SLOW circuit to the MAIN circuit (1/8 to
1/4) throttle. A smaller diameter will make
this range. TAPER (A) changes are only
made if there is a problem balancing the
calibration between 1/4 and 3/4 throttle. If
the mixture is rich at 1/4 throttle and lean at
3/4 throttle , a JET NEEDLE with a larger
taper is needed. If mixture is lean at 1/4
throttle and rich at 3/4 throttle change to
smaller taper. If the calibration is lean from
1/4 to 3/4 throttle, raise the JET NEEDLE
by lowering clip position, or use JET NEEDLE
with shorter length (L1). If the calibration is
rich, lower the JET NEEDLE with a longer
(L1).
5) WIDE OPEN THROTTLE
Changiing the MAIN JET affects this range.
SELECT the size of MAIN JET which offers the
best W.O.T. performance, then install one,
size larger MAIN JET for ideal engine
durability.
6) ACCELERATOR PUMP (FOR FCR)
In normal applications, the ACCELERATOR
PUMP should not require any adjustment. If
a rich stumble occurs as the throttles are
opened, the ACCELERATOR PUMP timing
can be delayed by widening the gap on the
ACCELERATOR PUMP linkage where it
makes contact with the plastic lever.
Reducing the gap will cause the
ACCELERATOR PUMP to deliver fuel
earlier.
7) THROTTLE VALVE CUT-AWAY
(FOR CR, PWK, PJ, & PE)
THROTTLE VALVE CUT-AWAY will
inluence the calibration in the are of 1/8 to
1/4 throttle. What the CUT-AWAY does is
change the air velocity over the MAIN
NEEDLE JET which changes when the
MAIN SYSTEM begins delivering fuel. If the
transition us lean change the throttle valve to
a valve which has less CUT-AWAY (lower
number) if this range use a throttle
cvalve with more valve CUT-AWAY (higher
number).
DIAMETER
TAPER
CLIP POSITION
N427-OC
N427-OC
N427-OC
DIAMETER (mm)
DIAMETER (mm)
DIAMETER (mm)
THROTTLE OPENING (FCR 39)
THROTTLE OPENING (FCR 39)
THROTTLE OPENING (FCR 39)
3
2.5
2
1.5
3
2.5
2
1.5
3
2.5
2
1.5
Jet Needle Changes
Carburetor Tuning
531