7-4
ENGINE
ROAD CONDITION AND EXAMPLES OF CARBURETOR SETTING
A. For USA and CDN
B. Except for USA and CDN
SPECIFICATIONS OF JET NEEDLE
EXAMPLES OF CARBURETOR SETTING DEPENDING ON SYMPTOMGeneral condition Sandy condition
Under 10°C
(50°F)15–25°C (59–
77°F)Over 30°C
(86°F)Under 10°C
(50°F)15–25°C (59–
77°F)Over 30°C
(86°F
(Winter) (Spring, Au-
tumn)(Summer) (Winter) (Spring, Au-
tumn)(Summer)
Main jet #440 #430 #420 #460 #450 #440
Jet needle 6BFY44-74-3 6BFY43-74-3 6BFY44-74-2 6BFY43-74-4 6BFY44-74-3 6BFY43-74-3
Pilot jet A #42.5 #40 #40 #42.5 #40 #40
B #47.5 #45 #42.5 #47.5 #45 #42.5
Pilot air screw 2-1/4 2-1/4 2-1/4 2-1/4 2-1/4 2-1/4
Diameter of straight portion
ø2.72 mm
(0.1071 in)ø2.73 mm
(0.1075 in)ø2.74 mm
(0.1079 in)ø2.75 mm
(0.1083 in)ø2.76 mm
(0.1087 in)
Rich 1 richer 6BFY43-72-4 6BFY43-73-4 6BFY43-74-4 6BFY43-75-4 6BFY43-76-4
0.5 richer6BFY44-72-3 6BFY44-73-3 6BFY44-74-3 6BFY44-75-3 6BFY44-76-3
6BFY42-72-4 6BFY42-73-4 6BFY42-74-4 6BFY42-75-4 6BFY42-76-4
STD 6BFY43-72-3 6BFY43-73-3 6BFY43-74-3 6BFY43-75-3 6BFY43-76-3
0.5 leaner6BFY44-72-2 6BFY44-73-2 6BFY44-74-2 6BFY44-75-2 6BFY44-76-2
6BFY42-72-3 6BFY42-73-3 6BFY42-74-3 6BFY42-75-3 6BFY42-76-3
Lean 1 leaner 6BFY43-72-2 6BFY43-73-2 6BFY43-74-2 6BFY43-75-2 6BFY43-76-2
Symptom Setting Checking
At full throttle
Stall at high speeds
*Hard breathing
Shearing noise
Whitish spark plug
↓
Lean mixtureIncrease main jet calibration no. (Gradual-
ly)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
At full throttle
Stop of speed pick-up
Slow speed pick-up
Slow response
Sooty spark plug
↓
Rich mixtureDecrease main jet calibration no. (Gradual-
ly)
*In case of racing slight enrichment of mix-
ture reduces engine trouble.Discoloration of spark plug→If tan color, it
is in good condition.
If not effect:
Clogged air filter
Fuel overflow from carburetor
Clogged main air passage or clogged fil-
ter
