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Carburettor
Functioning, Basic setting, Final setting
WARNING! Do not start the saw without the bar,
chain and clutch cover (chain brake) assembled.
If you do, the clutch might come loose and
cause severe injuries.
Operation
• The carburettor governs the engine speed via the throttle. Air/
fuel are mixed in the carburettor. The air/fuel mixture is
adjustable. To take advantage of the saw’s maximum output the
setting must be correct.
• Adjusting the carburettor means the engine is adapted to local
operating conditions, e.g. climate, altitude, petrol and the type of
2-stroke oil used.
• The carburettor has three
adjustment possibilities:
L = Low speed jet.
H = High speed jet.
T = Adjustment screw for
idling.
• The fuel quantity required in relation to the air flow, provided by
opening the throttle, is adjusted by the L and H-jets. If they are
screwed clockwise the air/fuel ratio becomes leaner (less fuel)
and if they are turned anti-clockwise the ratio becomes richer
(more fuel). A leaner mixture gives a higher engine speed and a
richer mixture give a lower engine speed.
• The T screw regulates the idling speed. If the screw T is turned
clockwise this gives a higher idling speed; anti-clockwise a lower
idling speed.
Basic setting and running in
The carburettor is adjusted to a basic setting when the saw is
tested at the factory.
61: The basic setting is: H = 1 turns respective
L = 1 turns.
268: The basic setting is: H = 1 turns respective
L = 1 turns.
272XP: The basic setting is: H = 1 turns respective
L = 1 turns.
To provide the engine’s components with a good level of
lubrication (running in) the carburettor should be set for a
richer fuel mixture for the first 3-4 hours of operating. To
obtain this adjust the overspeed 6-700 rpm under the
recommended max. overspeed.
If you do not have the possibility to check the overspeed using a
tachometer the H-jet should not be set for a leaner mixture than
that stated for the basic setting. The recommended overspeed
should not be exceeded. NOTE! If the chain rotates while idling
the T screw should be adjusted anti-clockwise until it stops.
Fine adjustment
• When the saw has been ”run-in” the carburettor should be finely
adjusted. The fine adjustment should be carried out by
qualified person. First adjust the L-jet, then the idling screw T
and then the H-jet.
The following engine speed applies:
Max. overspeed Idling speed
61: 12.000 rpm 2.500 rpm
268: 12.500 rpm 2.500 rpm
272XP: 13.500 rpm 2.500 rpm
Conditions
• Before any adjustments are made the air filter should be clean
and the cylinder cowling fitted. Adjusting the carburettor while a
dirty air filter is in use will result in a leaner mixture when the filter
is finally cleaned. This can give rise to serious engine damage.
• Carefully turn the L and H-jets clockwise to the bottom. Now turn
the jets one turn anti-clockwise. The carburettor is now set to H =
1 and L = 1.
• Now start the saw according to the starting instructions and run it
warm for 10 minutes.
NOTE! If the chain rotates the T screw should be turned anti-
clockwise until the chain stops.
• Place the saw on a flat surface so that the bar points away from
you and so that the bar and chain do not come into contact with
the surface or other objects.
Low speed needle L
Try to find the highest idling
speed, turning the low speed
needle L clockwise respectively
counter-clockwise. When the
highest speed has been found,
turn the low speed needle L 1/4
turn counter-clockwise.
NOTE! If the chain rotates in
the idling position, turn the
idling speed screw counter-
clockwise until the chain stops.
Final setting of the idling speed T
Adjust the idling speed with the screw T. If it is necessary to re-
adjust, first turn the idle speed adjusting screw T clockwise, until
the chain starts to rotate. Then turn, counter-clockwise until the
chain stops. A correctly adjusted idle speed setting occurs when
the engine runs smoothly in every position. It should also be good
margin to the rpm when the chain starts to rotate.
Contact your servicing dealer, if the idle speed
setting cannot be adjusted so that the chain
stops. Do not use the saw until it has been
properly adjusted or repaired.
High speed needle H
The high speed needle H
influences the power of the
saw. A too lean adjusted high
speed needle H (high speed
needle H closed too much)
gives overrevs and damages
the engine. Let the saw run at
full speed for about 10 seconds.
Thereafter, turn the high speed
needle H 1/4 turn counter-
clockwise.
Let the saw run again at full
speed for about 10 seconds and note the difference of the engine-
sound. Repeat this procedure with the high speed needle H turned
1/4 turn more counter-clockwise. The saw has now been tested
with the following settings: H=±0, H=+1/4, H=+1/2 from basic
adjustment. At full speed the engine has produced a different
sound for each setting. The high speed needle H is correctly set
when the saw ”4-cycles” a little. If the saw ”whistles” the setting is
too lean. If there is too much exhaust gas at the same time as the
saw ”4-cycles” much, the setting is too rich. Turn the high speed
needle H until the setting sounds correct. NOTE! For optimum
setting of the carburettor, contact a qualified servicing dealer
who has a revolution counter at his disposal. The maximum
speed recommended must not be exceeded.
Correctly adjusted carburettor
A correctly adjusted carburettor means that the saw accelerates
without hesitation and the saw 4-cycles a little at max speed.
Furthermore, the chain must not rotate at idling. A too lean
adjusted low speed needle L may cause starting difficulties and
bad acceleration.
A too lean adjusted high speed needle H gives lower power=less
capacity, bad acceleration and/or damage to the engine.
A too rich adjustment of the two speed needles L and H gives
acceleration problems or too low working speed.
!
MAINTENANCE
L
+ 1/4
!
H