Honda C65 - Honda Motorcycle Frame and Chassis Service

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3. ENGINE
Air screw stop spring
Figure 3- 102. Air screw
Ma in Je t
Fi gure 3- 103.
-...;;:!!!!!!!! " !!Jii · """:"ii: . .. ~~ .. Xl!/!1/{
(li ., f/l:
Needle Je t ho lder
g. Air screw
The air screw reg ula es he amount of air m1x1 ng
with the fuel in the slow sp ee d system by contro lling
the amount of pilot
air m ixin g wit h the fuel whi ch had
ent
ered from the sl ow jet. In hi s way , t he prope r
fuel air mixture is mainta ined (Fig. 3-1 02)
Turning the a ir sc r ew in w ill produ ce a rich fuel
air mixtu re and backing off on the screw wi ll result
in a
lean mixture.
6. ADJUSTING THE CARBURETOR
a. High speed a d j ustment
can be ob tain ed w ith
an i nd icat ion that the
·s od ;usied lean, the re fore, the main je t
~ a ce o•og ess ive ly r ep lac ed with a j et of a l arger
S: =e o~.o •e ·es:ed o ob a in the cor rect size.
e)
-e ~a j e' number sizes below ~100 are 98, 95,
-.2 0, and the si zes above ~ 100 are 11 0, 115
"d incr eases at an inte rval of 5. (Fig. 3- 1 03)
= ·' e s peed drops when the choke va l ve is closed,
i: is on ind ic ation that the main jet is either of the
corr ec si ze or too large. The de termi nation is
ode by the fol l owing procedu re.
0 The Corre ct Main Jet
A
ft er the main jet h ad been ch ange to one of
o sm a ll er size, it is found that the speed decreases
ond
upon closing the choke a sma ll amoun t, t he sp eed
in creases, it is an in di cat i on that the main jet wh ich
h
ad been ins ta lled is t oo sma ll in size. The main
j
et shou ld be repl aced aga in w it h the or i ginal ma in
j
et whic h con be assumed to be of the co rr ect size.
0 To o Large a Main Jet
Repl
ace the main jet progressively with one of
a smaller size unt il t he condi t ion in the previous
sect ion occ urs.
b. Adju sti ng the Inte r med i ate Sp eed
The fuel mixtu re adj ustment between the t hrott le
ope ning 78 to % is a cco mplished mainly by selecting
the steps on the needle jet and also by the c ut-away
on the t hrott le va l ve . However , it is not pra ct ica l to
adjust
only the intermediate s pe ed wi th the cut- awa y
of the t hrott le val ve since the cut-away e ff ects t he
ra n ge of throttle between 31{. to Jtr, opening. In the
in termediate range, the jet nee dle shou ld be in the
lower positi on for good fuel economy provided that
the accele r at i on is good :