Jonsered 2141 - Manual (Page 29)

English –
29
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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.
• The satisfactory operation of a catalytic converter depends,
among other factors, on the correct adjustment of the
carburettor. Follow carefully the instructions below, using a
tachometer to check engine speed.
• 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. The basic setting is: H = 1 turn respective L = 1 turn.
To provide the engine’s components with a good level of lubrica-
tion (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 speed 600-700 rpm under the recommended max. speed.
If you do not have the possibility to check the speed using a tachom-
eter the H-jet should not be set for a leaner mixture than that stated for
the basic setting.
The recommended speed 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. speed Idling speed
2141 12 500 rpm 2 700 rpm
2145 12 500 rpm 2 700 rpm
2150 12 500 rpm 2 700 rpm
Changing the type of fuel
Fine tuning may be required if the chain saw, after changing the type of
fuel, performs differently with regard to starting, acceleration, max.
speed, etc.
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MAINTENANCE
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 enginesound.
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.
L
+ 1/4
H
! WARNING! The catalytic converter muffler gets
very hot during and after use. This also applies
during idling. Be aware of the fire hazard, especially
when handling the saw near flammable substances
or vapours.
H
H L
T