Troy-Bilt 8 HP - Manual (Page 57)

Carburetor adjustments
The carburetor provides the en­
gine’s com bustion cham ber w ith
the correct air-fuel ratio for a w ide
range of operating conditions.
The factory settings should be
correct for average operating condi­
tions and you should avoid m aking
unnecessary adjustm ents. H ow ­
ever, if you feel that an adjustm ent
is needed to com pensate for differ­
ences in fuel, tem perature, altitude
or load, please refer to the follow ­
ing recom m ended adjustm ents.
A,
WARNING
K eep cigarettes, sparks, and open
flam es aw ay from the carburetor
and fuel system to prevent the pos­
sibility of a fire or explosion.
IMPORTANT
The carburetor adjusting screw s
are needle valves w hich taper to
critical dim ensions. These screw s
can be dam aged if they are turned
in forcefully.
A
WARNING
D o not operate the engine in an
enclosed or poorly ventilated area.
E ngine exhaust gases contain car­
bon m onoxide, an odorless, taste­
less, and deadly poison.
7 HP Briggs & Stratton:
1. W ith the engine stopped, gently
turn the H igh S peed N eedle Valve
and Throttle Idle M ixture V alve
clockw ise until they just close.
The valves m ay be dam aged by
turning them too far. See Figure
6-61.
2. N ow open H igh Speed N eedle
V alve IV 2 turns counterclockw ise
and Throttle Idle M ixture V alve one
turn counterclockw ise. This initial
adjustm ent w ill perm it the engine
to be started.
3. S tart engine and allow to w arm
for a few m inutes prior to final
adjustm ent. N O TE : The air cleaner
m ust be assem bled to carburetor
w hen running the engine.
4. P lace the throttle lever on the
handlebar in the “FA S T” position.
Turn the H igh S peed N eedle V alve
clockw ise until engine slow s (lean
m ixture). Then turn it out past the
sm ooth operation point (rich m ix­
ture). N ow turn the needle valve to
a m idpoint setting betw een rich
and lean.
5. A djust the idle R P M as follow s;
(a) R otate the throttle counter­
clockw ise and hold it against
the Throttle S top w hile adjust­
ing the Throttle Idle S peed
A djusting S crew to obtain 1750
R PM . Turn screw in for faster
idle; out for slow er idle.
(b) W hile still holding throttle
against Throttle Stop, turn
Throttle Idle M ixture V alve in
(lean) and out (rich). S et valve
at m idpoint betw een rich and
lean. R elease throttle. If engine
w ill not accelerate properly, the
carburetor should be read­
justed, usually to a slightly
richer m ixture.
8 HP Kohler:
1 . W ith the engine stopped, turn
the M ain Fuel and Idle Fuel adjust­
ing screw s clockw ise, until they
bottom lightly (P hoto 6-62).
2. P relim inary S etting— M ain Fuel
S crew ; Turn the M ain Fuel S crew
out 2 full turns from bottom .
3. P relim inary S etting— Idle Fuel
S crew : Turn the Idle Fuel S crew
out 1V 4 turns from bottom .
4. Final S etting— M ain Fuel S crew :
P lace the W heels/Tine/P TO D rive
Lever in “N EU TR A L” and start the
engine. Let it run at half-throttle
speed for 5-10 m inutes. M ove the
throttle lever to the “FA S T” posi­
tion and then turn the M ain Fuel
S crew clockw ise until the engine
starts to lose speed (too lean a
m ixture). N ow , count the turns as
you turn the screw counterclock­
w ise until the engine begins to run
unevenly (too rich a m ixture). Turn
the screw clockw ise to a point m id­
w ay betw een the too lean and too
rich m ixtures. That position, or
turning the screw counterclock­
MAIMTIKAICE AND SERVICE
w ise about V 2 turn m ore, should be
the proper setting for tilling.
5. Final S etting— Idle Fuel S crew :
P lace the W heels/Tine/P TO D rive
Lever in “N EU TR A L” and start the
engine. Let it run at half-throttle
speed for 5-10 m inutes. A llow the
engine speed to fall to idle, or put
the engine throttle in the idle posi­
tion. A djust the Idle Fuel S crew by
follow ing the sam e procedure de­
scribed in S tep 4. The recom ­
m ended idle speed should not
exceed 1500 R PM (R evolutions P er
M inute)f
6. Idle S peed Setting: Place
the W heels/Tine/P TO D rive Lever
in “N EU TR A L” and start the engine.
Let it run at half-throttle for 5-10
m inutes. A llow the engine speed to
fall to idle, or put the engine throt­
tle in the idle position. A djust the
engine idle speed to the desired
R PM * by turning the Idle S peed
S crew clockw ise or counter­
clockw ise. A llow several seconds
betw een each adjustm ent for the
engine to adapt to each new setting.
‘Typical idle speed is 1200 R PM .
6-61: 7 HP Briggs & Stratton Engine
carburetor.
'V
(
iti .
M A IN FU EL
ID LE S PE E D H
ID LE FU E L.
6-62: 8 HP Kohler Engine carburetor
(air cleaner components removed for
photo clarity).
55