26 –
English
MAINTENANCE
Carburettor
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.
Carburettor 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 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 setting
•
The basic carburettor 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.
The basic setting can vary between: H = 1 - 1 1/4 turns
and L = 1 - 1 1/4 turns.
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:
2700 rpm
CAUTION!
The machine should only be run for short periods
at its highest speed. For optimum adjustment of the
carburettor, contact a qualified dealer/service workshop that
has a revolution counter at their disposal.
Recommended max. speed:
See the Technical data section.
During the running-in period (8-10 tanks of fuel) the maximum
speed should be set 600-700 rpm below the recommended
maximum speed (= open the high speed jet H a further 1/8
turn).
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 idle speed by turning the low speed jet
L clockwise then anti-clockwise. When the highest speed has
been found, turn the low speed jet L 1/4 turn anti-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
GR41/50 RS44
RS52
!
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
+ 1/4
