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Carburettor adjustment
The carburettor can be designed in different ways, depending
on existing environmental and emissions legislation. Some
chain saws are equipped with movement limiters on the
carburettor’s adjuster screws. These limit the adjustment
possibilities to a maximum of a 1/2 turn.
When your chain saw is equipped with a carburettor that
features movement limiters, the carburettor should be
adjusted according to the instructions under the heading
Carburettor with movement limiters.
When your chain saw is equipped with a carburettor that does
not feature movement limiters, the carburettor should be
adjusted according to the instructions under the heading
Carburettor without movement limiters.
Contact your servicing dealer (retailer) if you are
uncertain of which type of carburettor your chain saw is
equipped with.
Carburettor with movement limiters
Your Jonsered product has been designed and manufactured
to specifications that reduce harmful exhaust fumes.
Function, Basic settings, Fine adjustment
Function
• The carburettor governs the engine’s speed via the
throttle control. Air and fuel are mixed in the carburettor.
The air/fuel mixture is adjustable. Correct adjustment is
essential to get the best performance from the machine.
• Adjusting the carburettor means that the engine is
adapted to local operating conditions, e.g. climate,
altitude, petrol and the type of 2-stroke oil.
• The carburettor 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 settings and running in
The basic carburettor settings are adjusted during testing at
the factory. Avoid running at a too high speed during the first
10 hours.
CAUTION! If the chain rotates while idling the T-screw
must be turned anti-clockwise until the chain stops.
Rec. idle speed: 2700 rpm
Fine adjustment
When the machine has been ”run-in” the carburettor 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.
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, maximum speed, etc.
Conditions
• Before any adjustments are made the air filter should be
clean and the cylinder cover fitted. Adjusting the
carburettor while a dirty air filter is in use will result in a
leaner mixture next time the filter is cleaned. This can give
rise to serious engine damage.
• 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 chain rotates while idling the T-screw must be
turned anti-clockwise until the chain stops.
• Place the machine 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.
!
WARNING! Do not start the chain saw unless
the bar, chain and clutch cover (chain brake)
are fitted, otherwise the clutch may come
loose and cause personal injury.
1/2
1/2
H
L
H
L
1/2
1/2
H
L
!
WARNING! Contact your servicing dealer, if
the idle speed setting cannot be adjusted so
that the chain stops. Do not use the chain
saw until it has been properly adjusted or
repaired.
L
H
T