Stihl HT 75 Instruction Manual - Page 31

Standard Setting, Fine Tuning, Adjusting Idle Speed, At high altitude

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english Standard Setting : Shut off the engine. : Check chain tension. : Check the air filter and clean or replace as necessary. : Check spark arresting screen* and clean or replace as necessary. : Check adjustment of the throttle cable and readjust if necessary - see "Adjusting the Throttle Cable". : Turn high speed screw (H) counterclockwise (max. 3/4 turn) as far as stop. : Carefully screw the low speed screw (L) down onto its seat. Then open it one turn counterclockwise. : Start and warm up the engine. : Adjust idle speed with the idle speed screw (LA) so that the chain does not rotate. Fine Tuning A slight correction of the setting of the high speed screw (H) may be necessary if engine power is not satisfactory when operating at high altitude or at sea level. Rule of thumb : Turn high speed screw (H) about 1/4 turn for every 1000m (3300 ft) change in altitude. Conditions for adjustment : Carry out standard setting. : Warm up engine for about 5 minutes. : Open the throttle wide. At high altitude : Turn high speed screw (H) clockwise (leaner) no further than stop until there is no noticeable increase in engine speed. At sea level : Turn high speed screw (H) counterclockwise (richer) no further than stop until there is no noticeable increase in engine speed. It is possible that maximum engine speed may be reached with the standard setting in each case. Adjusting Idle Speed It is usually necessary to change the setting of the idle speed screw (LA) after every correction to the low speed screw (L). : Warm up engine for about 5 minutes. Engine stops while idling : Turn idle speed screw (LA) slowly clockwise until the engine runs smoothly - chain must not rotate. Chain rotates when engine is idling : Turn idle speed screw (LA) slowly counterclockwise until chain stops rotating and then turn the screw about another 1/2 to 1 turn in the same direction. Erratic idling behavior, engine stops even though setting of LA screw is correct, poor acceleration Idle setting too lean: : Turn low speed screw (L) counterclockwise (about 1/4 turn) until the engine runs and accelerates smoothly. * see "Guide to Using this Manual" 30 HT 70, HT 75

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30
english
HT 70, HT 75
Standard Setting
:
Shut off the engine.
:
Check chain tension.
:
Check the air filter and clean or
replace as necessary.
:
Check spark arresting screen* and
clean or replace as necessary.
:
Check adjustment of the throttle
cable and readjust if necessary –
see "Adjusting the Throttle Cable".
:
Turn high speed screw
(H)
counterclockwise
(max. 3/4 turn)
as far as stop.
:
Carefully screw the low speed
screw
(L)
down onto its seat. Then
open it
one
turn counterclockwise.
:
Start and warm up the engine.
:
Adjust idle speed with the idle speed
screw
(LA)
so that the chain does
not rotate.
Fine Tuning
A slight correction of the setting of the
high speed screw
(H)
may be necessary
if engine power is not satisfactory when
operating at high altitude or at sea level.
*
see "Guide to Using this Manual”
Rule of thumb
:
Turn high speed screw
(H)
about
1/4 turn for every 1000m (3300 ft)
change in altitude.
Conditions for adjustment
:
Carry out standard setting.
:
Warm up engine for about 5
minutes.
:
Open the throttle wide.
At high altitude
:
Turn high speed screw
(H)
clock-
wise (leaner) no further than stop
until there is no noticeable increase
in engine speed.
At sea level
:
Turn high speed screw
(H)
counter-
clockwise (richer) no further than
stop until there is no noticeable
increase in engine speed.
It is possible that maximum engine
speed may be reached with the
standard setting in each case.
Adjusting Idle Speed
It is usually necessary to change the
setting of the idle speed screw
(LA)
after every correction to the low speed
screw
(L)
.
:
Warm up engine for about 5
minutes.
Engine stops while idling
:
Turn idle speed screw
(LA)
slowly
clockwise until the engine runs
smoothly – chain must not rotate.
Chain rotates when engine is idling
:
Turn idle speed screw
(LA)
slowly
counterclockwise until chain stops
rotating and then turn the screw
about another 1/2 to 1 turn in the
same direction.
Erratic idling behavior, engine stops
even though setting of LA screw is
correct, poor acceleration
Idle setting
too lean:
:
Turn low speed screw
(L)
counterclockwise (about 1/4 turn)
until the engine runs and
accelerates smoothly.