Honda C65 - Jet Needle; Throttle Valve; Slow Jet

3.7 CARBURETOR
-=· -.=:--=.. =
-~ :· ·:eo e in con juncrio · -· e ·eeo e j et
:::: - =~= e::- · er, regu lates e .e -- - ~"e at th e
-,--:-::. ::-e - rottl e ope ning p(·::· be iw een ~
- _ ---~ - e o pen ing!. The l ong · ooered jet n eed le
- ·::::-eo cent rally w i th in he cen · er hol e of the
--·::- e :alv e and w ith the ope red end in serted into
··e ·eed le jet. The vertica l mov ement of the throttle
a .e o w hich the jet n eed le is attached co nt ro ls the
"o" o f the fuel in respect to the throttle ope ning to
affor d a co rr ect fuel mixt ure ratio. There are five
nee dl e clip grooves !w hich are counted from the to pl
to reg ulat e the richness of the fuel mi x ture. The fuel
m ixture becomes richer as the clip is m ove d progre s-
siv ely from the No . 1 groove to the No . 5 groove.
(Fig. 3- 99)
e. Throttle valve
The function of the throttle valve is to co n tr ol
the amount of air token into the engine which serves
to increase the engine RPM and the po w er outpu t,
and
in addition, performs the important fu nction of
cont rolling the fuel air mi xture . (Fig. 3-1 00)
The thr o ttle valve is cut-a w ay on the air inl et
side. By c
hanging the size of the cut-a way (designated
by cut-away No.l the p re ss u re actuat ing the ne edle
va lve ca n be altered to change the amount of fu el
now and causes a change to the fue l mixture. The
va lve with a large r c ut - away number will produce a
leaner fuel m ix tu re. However, the range of its effec-
tiveness is mainly at low speed from idling speed to
ap proximately ~ thr o ttle open ing. It has no effect
beyond ;% thrott le opening.
The throttle valve is normally oper a ted by the
throttle cab le attached to the top of the carburetor.
A throttle stop screw keeps the throttle va lve in th e
idle position.
Turn ing the stop screw in will cause the throttle
valve to rise, and backing off o n the st op screw w il l
l
ower the th ro ttl e valve .
(Caution)
The throttle valve guide groove serves as a
junction for the throttle cable and the thro ttle
valve and also to maintain the throttle valve in the
correct relative position within the carburetor,
therefore , if it is r eve rsed, th e cut-away w il l be on
the wrong s id e and will resu lt in rich fuel mixture
as well as causing insuffici ent eng in e speed .
f. Slow jet
The slow jet regula tes the fue l now during idling
and small throttle opening, and permits th e air to ent er
th rough the a ir bleed to mi x with the fuel for
at om izati o n.
The sl
ow j et is similar to th e main jet in that the
larger the je t size number, the greater will be the
fuel now and consequen tl y a richer fuel air mi x tu r e.
(Fig. 3-101)
Figure 3-99. Jet needle
Figure
3-100 . Throttle valve
Figure 3- 10 1. S low jet
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