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BASIC CARBURATOR SETTING
Type
Keihin FCR-MX 37
Keihin FCR-MX 37
Keihin FCR-MX 39
Keihin FCR-MX 41
Carburator-setting number
3700A
3700A
3900A
4122A
Main jet
160
160
178
185
Jet needle
OBETP
OBEKT
OBDVR
OBDTP
Idling jet
42
42
42
40
Main air jet
200
200
200
200
Idling air jet
100
100
100
100
Needle position
3. rd from top
3. rd from top
3. rd from top
4. rd from top
Starting jet
85
85
85
85
Mixture control screw open
1,25
0,75
1,25
1
Slide
15
15
15
15
Performance restrictor
–
Slide stop
Slide stop
–
Stop pump membrane
858 / 2,15 mm
858 / 2,15 mm
858 / 2,15 mm
858 / 2,15 mm
Hot start device
–
–
–
2,2 mm
250 EXC RACING
Six Days
250 EXC RACING
11 kW
450 EXC RACING
12 kW
450 SX RACING
BASIC CARBURATOR SETTING
Type
Keihin FCR-MX 39
Keihin FCR-MX 39
Keihin FCR-MX 41
Carburator-setting number
3900A
3900B
4125A
Main jet
178
178
185
Jet needle
OBDTN
OBDVT
OBDTP
Idling jet
42
42
42
Main air jet
200
200
200
Idling air jet
100
100
100
Needle position
2. rd from top
3. rd from top
4. rd from top
Starting jet
85
85
85
Mixture control screw open
1,5
1,25
1,5
Slide
15
15
15
Performance restrictor
–
Slide stop
–
Stop pump membrane
858 / 2,15 mm
858 / 2,15 mm
858 / 2,15 mm
Hot start device
–
–
2,5 mm
525 EXC RACING
Six Days
525 EXC RACING
525 MXC RACING
12 kW
525 SX RACING
ENGLISH
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