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YAMAHA YZ250F(D) Owner's Service Manual Page 190

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SPECIFICATIONS OF JET NEEDLE
For USA, CDN, AUS, NZ and ZA
Rich
1 richer
0.5 richer
STD
0.5 leaner
Lean
1 leaner
For EUROPE
Rich
1 richer
0.5 richer
STD
0.5 leaner
Lean
1 leaner
EXAMPLES OF CARBURETOR SETTING DEPENDING ON SYMPTOM
Symptom
At full throttle
Hard breathing
Shearing noise
Whitish spark plug
Lean mixture
At full throttle
Speed pick-up stops
Slow speed pick-up
Slow response
Sooty spark plug
Rich mixture
Lean mixture
Rich mixture
1/4–3/4 throttle
Hard breathing
Lack of speed
1/4–1/2 throttle
Slow speed pick-up
Poor acceleration
Rich
N
P
NFPN-6
NFPP-6
NFLN-6
NFLP-6
NFPN-5
NFPP-5
NFLN-5
NFLP-5
NFPN-4
NFPP-4
Rich
M
N
NFPM-6
NFPN-6
NFLM-6
NFLN-6
NFPM-5
NFPN-5
NFLM-5
NFLN-5
NFPM-4
NFPN-4
Setting
Increase main jet calibration no. (Gradual-
ly)
Decrease main jet calibration no. (Gradual-
ly)
Lower jet needle clip position. (1 groove
down)
Raise jet needle clip position. (1 groove up)
Lower jet needle clip position. (1 groove
down)
Raise jet needle clip position. (1 groove up)
Diameter of straight portion
Q
R
NFPQ-6
NFPR-6
NFLQ-6
NFLR-6
NFPQ-5
NFPR-5
NFLQ-5
NFLR-5
NFPQ-4
NFPR-4
Diameter of straight portion
P
Q
NFPP-6
NFPQ-6
NFLP-6
NFLQ-6
NFPP-5
NFPQ-5
NFLP-5
NFLQ-5
NFPP-4
NFPQ-4
Discoloration of spark plug → If tan color, it
is in good condition.
If cannot be corrected:
Clogged float valve seat
Clogged fuel hose
Clogged fuel cock
Check that the accelerator pump operates
smoothly.
Discoloration of spark plug → If tan color, it
is in good condition.
If cannot be corrected:
Clogged air filter
Fuel overflow from carburetor
Groove 1
Groove 2
Groove 3
Groove 4
Groove 5
Groove 6
Groove 7
Jet needle
The clip position is the jet needle groove on
which the clip is installed.
The positions are numbered from the top.
Check that the accelerator pump operates
smoothly. (except for rich mixture symp-
tom).
7-4
ENGINE
S
T
NFPS-6
NFPT-6
NFLS-6
NFLT-6
NFPS-5
NFPT-5
NFLS-5
NFLT-5
NFPS-4
NFPT-4
R
S
NFPR-6
NFPS-6
NFLR-6
NFLS-6
NFPR-5
NFPS-5
NFLR-5
NFLS-5
NFPR-4
NFPS-4
Checking
Clip
Leaner
(Standard)
Richer
Lean
U
NFPU-6
NFLU-6
NFPU-5
NFLU-5
NFPU-4
Lean
T
NFPT-6
NFLT-6
NFPT-5
NFLT-5
NFPT-4

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  • rodrigo Dec 03, 2017 02:34:
    MUY INTERESANT​E EL MANUAL PORQUE AYUDA PARA TENER A PUNTO UN MOTOR BIEN ARMADO TAL COMO INDICA EL MANUAL.