Maintenance; Carburettor - Jonsered RS44/52 Operator's Manual

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.
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.
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.
• The setting of the carburetor means that the engine is
adepted to local conditions, for example, the climate,
altitude, fuel 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
RS44
• 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.
24 –
English

MAINTENANCE

RS52
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
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.
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 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.
+ 1/4
L
Fine adjustment of the idle speed T
Adjust the idle speed using the idle adjustment screw T, if it is
necessary to readjust. First turn the idle adjustment screw T
clockwise until the cutting attachment starts to rotate. Then
turn the screw anticlockwise until the cutting attachment
stops. The idle speed is correctly adjusted when the engine
will run smoothly in every position. The idle speed should also
be well below the speed at which the cutting attachment starts
to rotate.