Yamaha YZ450F(Y Owner's Manual page 181

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
Standard leak jet
CARBURETOR SETTING PARTS
Main jet
Rich #172
(STD) #160
Lean #148
Pilot jet
Rich
(STD)
#55
Lean
Jet needle
Rich NFPN 5TA-14916-PN
Lean NFPU 5TA-14916-PU
Rich NFLN 5TA-14916-LN
(STD) NFLR 5TA-14916-LR
Lean NFLU 5TA-14916-LU
Leak jet
Rich
(STD)
Lean
Size Part number
4MX-14943-92
#170 4MX-14943-41
#168 4MX-14943-91
#165 4MX-14943-40
#162 4MX-14943-90
4MX-14943-39
#158 4MX-14943-89
#155 4MX-14943-38
#152 4MX-14943-88
#150 4MX-14943-37
4MX-14943-87
Size Part number
#52 4MX-14948-08
#50 4MX-14948-07
#48 4MX-14948-06
#45 4MX-14948-05
#42 4MX-14948-04
#40 4MX-14948-03
#38 4MX-14948-02
Size Part number
NFPP 5TA-14916-PP
NFPQ 5TA-14916-P1
NFPR 5TA-14916-PR
NFPS 5TA-14916-PS
NFPT 5TA-14916-PT
NFLP 5TA-14916-LP
NFLQ 5TA-14916-L1
NFLS 5TA-14916-LS
NFLT 5TA-14916-LT
Size Part number
#45 4JT-1494F-05
#50 4JT-1494F-07
#55 4JT-1494F-09
#60 4JT-1494F-11
#65 4JT-1494F-13
7-3
ENGINE