Main Jet/Air Jet/Needle Jet; Jet Needle; Throttle Valve; Operation Of P-50 Carburetor Component Parts - Honda P-50 Shop Manual

18
\
Fig.
3· 18
Mai n jet
•J,
Genuine parts mark
2:
M ain jet
NO.
3
Fig. 3-19 Jet needle
Ill
Needle clip
(2
Type mark and genuine parts mark
,j ,
Jet needl e
Ope ration of P-50 Carburetor Component
Parts
1.
Main Jet
It meters the fuel flow during full throttle con.
dition ( top speed) to provide
a
proper fuel mixtur e.
Not only does it function at top speed but it also is
effective to a certain degree at intermediate speed.
The larger the main jet size number, greater will be
the nozzle opening and consequently the fuel flow,
providing a richer fuel mixture. (Fig . 3 18)
2. A ir Jet
3.
During full throttle opening. the fuel mixture at
high eng ine speed w ill become rich. and at s low speed
the mixture becomes lean. To prevent such a cond i·
tion, air is bled into the main jet to maint ain a uni
form mi xture. The function of the air jet is to control
the amount of the blee d
<:~ir .
As t he air jet becomes larger, the arnollnt of ble-
ed air is increased. resul ting in a lean fuel mixture,
however, at a se t throttle opening, a high eng ine spe.
ed will produce a leaner mixture There is only a
small variation in fuel con sumption between high and
low eng ine speed.
Needle Jet
Dunng full or half throttle opening. the fue l which
had beet\ metered by the main jet is ag ain met ered
by
thd nee dle jet . The adju stment is per forme d in
conjucllon with the jet needle which is explained in
the following section. The needle jet openin g is made
exceptionally accurate for precise control.
4.
Jet Needle
The jet needle. in conjuction wi th the needle jet
described earlier. regulates the fuel mixture at the
int ermediate throttle opening (principdlly between
1 / 4 to
3/ 4
throttle opening ). The long t apered jet
needle is located within the center hole of the throt.
t ie valve w i th the tapered end insert ed into the
needle jet. The vertical movement of the thro ttle
valve to which the jet needle is attached controls
the flow of the fuel in r espect to the throttle open.
ing to afford a correct fuel mixture ratio.
There are five clip grooves ( which are counted
from the top) on the head of the jet needle to regulate
the richness of the fuel mixture.
The fuel mixture becomes richer as the clip is
moved progressi vely from the No. 1 g roove to the
No. 5 groove. (Fig. 3 19)
5.
Thr ottle Valve
The f unction of the throt ti e valve is to control
the amount of air taken into the engine : this det er -
mines t he engine spe ed. the power output, and in
ilddition. performs the impor tant func lion of con troJI.
ing the fuel air mixtu re.
The throttle valve has a cut -away on the air inlet
side.