Honda CB160 Shop Manual page 54

50
Fig.
3. 144
Replacing of main jet
Fig. 3. 1 A5
Chcn~ing step
:Of
jet needle
3. ENGINE
C. Adjustment
1. Adjustment at high speed
In the range from full throttle to l /2 throttle, ad-
justment of the mixture ratio is made by the mai'l jet.
(Refer to Fig.
3. 144)
Determinat:o:-r of mixture density is obtained by the
following methods.
a. At fuel throttle, if the speed is reduced by slightly
closing the choke, the mixed gas is too thin. In
such case, the main jet should be replaced with a
larger one and a condition check made.
b. If speed is reduced by closing the choke, the
main jet is suitable or is too large. Determination
is made by the following methods.
(]} When the main jet is suitable: When a smaller
main jet is employed and speed decreases, and
when the choke is slightly closed and speed in-
creases, the new main jet (smaller one} is too
small. Hence, the original one is suitable.
12} When the main jet is too large : Gradually
smaller main jets should be employed in replace-
ment until the status dascribed in section I l} results.
2.
Adjustment at mid-throttle
Adjustment of the mixture in a range from
l
/8 to
l /2 throttle is mainly obtained by the jet needle steps
and the cutaway of the throttle valve. However, as
the cutway of the throttle valve infiuences the range
below l /8 throttle misadjustment is apt to occur.
For medium speed adjustment, as long as accelera-
tion characteristics are maintained, employment of a
smaller jet needle is more practical. (Refer to Fig.
3. 145)
a. Jet needle
Ill If abnormal btock smoke is ejected during
operation at medium speed, the mixture is too
heavy; the jet needle should be pulled up one step.
12) During engine braking after accelerating or
cruising when the engine sounds rough, the [et
needle clip should be lowered by one step.
b. Cutaway of throttle valve
When the throttle cutaway with a larger number
is employed, the mixture becomes thinner and vice
versa. The throttle vavle covers not only medium
speed, but also low speed in the range of adjust-
ment : taken while adjusting.
( l l Except for special cases such as racing, rep-
lacement of the cutaway is not required.