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MAINTENANCE
Carburetor
Your Jonsered product has been designed and manufactured
to specifications that reduce harmful exhaust fumes. The
engine will be run in after it has used 8-10 tanks of fuel. To
ensure that the engine runs at peak performance and
produces as little harmful exhaust fumes as possible after the
running-in period, ask your dealer/service workshop (which
has a rev counter for this purpose) to adjust your carburettor.
Carburetor adjustment
The carburettor can be designed in different ways, depending
on the existing environmental and emissions legislation.
Some machines are equipped with movement limiters on the
carburettor’s adjuster screws. These limit the adjustment
range to a maximum of 1/2 turn.
Function
• The carburetor governs the engine’s speed via the throttle
control. Air and fuel are mixed in the carburetor. The air/
fuel mixture is adjustable. Correct adjustment is essential
to get the best performance from the machine.
• The setting of the carburetor means that the engine is
adapted to local conditions, for example, the climate,
altitude, fuel and the type of 2-stroke oil.
• The carburetor has three adjustment controls:
L = Low speed jet
H = High speed jet
T = Idle adjustment screw
• The L and H-jets are used to adjust the supply of fuel to
match the rate that air is admitted, which is controlled with
the throttle. 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 lean
mixture gives a higher engine speed and a rich mixture
gives a lower engine speed.
• The T-screw regulates the throttle setting at idle speed. If
the T-screw is turned clockwise this gives a higher idle
speed; turning it anti-clockwise gives a lower idle speed.
Basic setting
• The basic carburetor settings are adjusted during testing
at the factory. The basic setting is richer than the optimal
setting and should be maintained for the first few hours the
machine is in use. The carburettor should then be finely
adjusted. Fine adjustment should be carried out by a
skilled technician.
CAUTION! If the cutting attachment rotates when the engine
is idling the idle adjustment screw T should be turned anti-
clockwise until the cutting attachment stops.
Rec. idle speed: See the Technical data section.
Rec. idle speed: See the Technical data section.
Fine adjustment
When the machine has been ”run-in” the carburetor should be
finely adjusted. The fine adjustment should be carried out
by a qualified person. First adjust the L-jet, then the idling
screw T and then the H-jet.
Conditions
• Before any adjustments are made, make sure that the air
filter is clean and the air filter cover is fitted. If you adjust
the carburettor when the air filter is dirty it will result in a
leaner mixture when the filter is finally cleaned. This can
lead to serious engine damage.
• Carefully turn both jets, L and H, so that they are midway
between fully screwed in and fully screwed out.
• Do not attempt to adjust the L and H jets beyond either
stop as this could cause damage.
• Now start the machine according to the starting
instructions and let it warm up for 10 minutes.
CAUTION! If the cutting attachment rotates when the engine
is idling the idle adjustment screw T should be turned anti-
clockwise until the cutting attachment stops.
Low speed jet 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.
CAUTION! If the cutting attachment rotates when the engine
is idling the idle adjustment screw T should be turned anti-
clockwise until the cutting attachment stops.
!
WARNING! The complete clutch cover and
shaft must be fitted before the machine is
started, otherwise the clutch can come loose
and cause personal injury.
1/2
1/2
H
L
!
WARNING! If the idle speed cannot be
adjusted so that the cutting attachment
stops, contact your dealer/service
workshop. Do not use the machine until it
has been correctly adjusted or repaired.
L
H