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Carburettor - Husqvarna 268K, 272K Operator's Manual

Husqvarna brush cutter operator's manual
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Carburettor

Operation, Basic settings, Fine tuning
!
WARNING! The power cutter must be correctly
assembled with cutting arm and cutting head
before you start (See chapter " Assembly ".)
Operation
• The carburettor governs the engine's speed via the throttle.
Air/fuel is mixed in the carburettor. The air/fuel mixture is
adjustable. To take advantage of the engine's optimal output
the adjustment must be correct.
• The setting of the carburettor means that the engine is
adapted to local conditions, for example, the climate, altitude,
petrol and the type of 2-stroke oil.
• The carburettor is equipped
with three adjustment
possibilities:
L = Low speed needle
H = High speed needle
T = Idle speed adjuster
screw
• The fuel quantity in relation to the air flow permitted by the
throttle opening is adjusted using the L and H-needles.
Turning the needles clockwise gives a leaner fuel mixture
(less fuel) and turning them anti-clockwise gives a richer fuel
mixture (more fuel). A leaner mixture gives high revs while a
richer mixture give less revs.
• The T-screw regulates the position of the throttle while the
engine is idling. Turning the screw clockwise gives a higher
idling speed while turning it anti-clockwise gives a lower idling
speed.
Basic setting
The carburettor is set to its basic setting when test run at the
factory.
The basic setting is H = 3/4 turn respective L = 1 turn.
The carburettor should be set for a richer fuel mixture
during the first 3–4 hours of use so that the engine parts
are given good initial lubrication (running-in). To set this,
adjust the maximum speed to 6-700 rpm under the
recommended maximum speed.
If you do not have the possibility of checking the maximum
speed with a tachometer, the H-needle must not be set for a
leaner mixture than stated for the basic settings.
The recommended maximum speed must not be exceeded.
NOTE! If the cutting disc rotates while the engine is idling the T-
screw should be turned anti-clockwise until the cutting disc
stops.
MAINTENANCE
Fine tuning
• When the machine has been run-in the carburettor is finely
tuned. Fine tuning should be carried out by trained
personnel. The L-needle is adjusted first, then the idling
screw T and finally the H-needle. The following speed
recommendations apply:
Max. speed
10,000 rpm
Conditions
• The air filter should be clean and the cylinder cover fitted
when all adjustments are made. If the carburettor is adjusted
with a dirty air filter a too lean fuel mixture is obtained the
next time the air filter is cleaned. This can result in serious
damage to the engine.
• Carefully screw (clockwise) the L and H needles until they
bottom. Then screw out (anti-clockwise) the needles one turn.
The carburettor now has the setting H = 1 and L = 1.
T
L H
• Start the power cutter as set out in the start instructions (see
section "Start and stop" ) and run the cutter warm for 10
minutes. NOTE! If the cutting disc rotates while the engine
is idling the T-screw should be turned anti-clockwise
until the cutting disc stops.
Low speed needle L
• Find the highest idling
speed by slowly screwing
the low speed needle
clockwise respective anti-
clockwise. When the
highest speed is found,
screw the L-needle 1/4 turn
anti-clockwise. NOTE! If the
cutting disc rotates while the
engine is idling the T-screw
should be turned anti-
clockwise until the cutting
disc stops.
Fine tuning idling T
Idling is set using the screw marked T. If adjustment is
necessary screw in (clockwise) the idling screw T with the
engine running until the cutting disc starts to rotate. Thereafter
open (anti-clockwise) until the disc stops rotating. The correct
idling speed is set when the engine runs smoothly in all
positions with a good margin to the speed when the disc starts
to rotate.
!
Idling speed
2,500 rpm
L
WARNING! If the idling speed cannot be
adjusted so that the disc stops, contact your
service workshop. Do not use the machine
until it has been correctly adjusted or repai-
red.
+ 1/4
17
English –

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