Yamaha YZ450F(X), Owner'S Service Manual

Page: 178 / 574

7-3
ENGINE
ADJUSTING THE LEAK JET
(ADJUSTING THE ACCELERATOR
PUMP)
The leak jet "1" is a setting part that
adjusts the flow of fuel discharged by
the accelerator pump. Since the ac-
celerator pump operates only when
throttle is open, the leak jet is used to
adjust a fuel mixture ratio for quick
throttle opening and is therefore dif-
ferent from other setting parts that ad-
just a fuel mixture for each throttle
opening (each engine speed).
1. When the engine breathes hard in
quick throttle opening, select a
leak jet having lower calibrating
No. than standard to enrich the
mixture. <Example> #70
→
#60
2. When rough engine operation is
felt in quick throttle opening, se-
lect a leak jet having higher cali-
brating No. than standard to lean
out the mixture. <Example> #55
→
#50
CARBURETOR SETTING PARTS
Standard leak jet #55
Main jet Size Part number
Rich #172 4MX-14943-92
#170 4MX-14943-41
#168 4MX-14943-91
#165 4MX-14943-40
#162 4MX-14943-90
(STD) #160 4MX-14943-39
#158 4MX-14943-89
#155 4MX-14943-38
#152 4MX-14943-88
#150 4MX-14943-37
Lean #148 4MX-14943-87
Pilot jet Size Part number
Rich #52 4MX-14948-08
#50 4MX-14948-07
#48 4MX-14948-06
(STD) #45 4MX-14948-05
#42 4MX-14948-04
#40 4MX-14948-03
Lean #38 4MX-14948-02
Jet needle Size Part number
Rich NFPN 5TA-14916-PN
NFPP 5TA-14916-PP
NFPQ 5TA-14916-P1
NFPR 5TA-14916-PR
NFPS 5TA-14916-PS
NFPT 5TA-14916-PT
Lean NFPU 5TA-14916-PU
Rich NFLN 5TA-14916-LN
NFLP 5TA-14916-LP
NFLQ 5TA-14916-L1
(STD) NFLR 5TA-14916-LR
NFLS 5TA-14916-LS
NFLT 5TA-14916-LT
Lean NFLU 5TA-14916-LU
Leak jet Size Part number
Rich #45 4JT-1494F-05
#50 4JT-1494F-07
(STD) #55 4JT-1494F-09
#60 4JT-1494F-11
Lean #65 4JT-1494F-13