Jonsered POWERLITE 50C - Manual (Page 30)

30 – English
MAINTENANCE
Carburettor
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.
• The setting of the carburettor 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
• 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.
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.
Low speed jet L
Turn the low speed jet L clockwise until it stops. If the engine
accelerates poorly or idles unevenly, turn the low speed jet L
anticlockwise until good acceleration and idling are achieved.
CAUTION! If the chain rotates while idling the T-screw
must be turned anti-clockwise until the chain stops.
Final setting of the idling speed T
Adjust the idle speed with the T-screw. If it is necessary to re-
adjust, turn the T-screw clockwise while the engine is running,
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.
High speed jet H
At the factory the engine is adjusted at sea level. When
working at a high altitude or in different weather conditions,
temperatures and atmospheric humidity, it may be necessary
to make minor adjustments to the high speed jet.
CAUTION! If the high speed jet is screwed in too far, it may
damage the piston/cylinder.
When test run at the factory, the high speed jet is set so that
the engine satisfies the applicable legal requirements at the
same time as achieving maximum performance. The
carburettor’s high speed jet is then locked using a limiter cap
in the fully screwed out position. The limiter cap limits the
potential to adjust the high speed jet to at most half a turn.
!
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.
!
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
!
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.