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English – 17
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MAINTENANCE
Carburettor
Operation, Basic settings, Fine tuning
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.
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 Idling speed
10,000 rpm 2,500 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.
• 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.
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.
!
WARNING! The power cutter must be correctly
assembled with cutting arm and cutting head
before you start (See chapter ”
Assembly
”.)
T
L
H
L
+ 1/4