Husqvarna 356 BT X-series - Manual (Page 14)

14 – English
MAINTENANCE
Carburetor
Your Husqvarna product has been designed and
manufactured to specifications that reduce harmful
emissions. After the engine has used 8-10 tanks of fuel the
engine will be run-in. To ensure that it continues to run at peak
performance and to minimise harmful exhaust emissions
after the running-in period, ask your dealer/service workshop
(who will have a rev counter at their disposal) to adjust your
carburettor.
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.
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.
Low speed jet L
If the engine run unstable on idle, adjest the L jet clockwise
respectively anticlockwise until the engine runs smoothly.
Fine adjustment of the idle speed T
Adjust the idle speed screew T clockwise respectively anti-
clockwise until an idle speed of 2300 rpm is reached.
High speed jet H
Apply full throttle. Adjust the H jet clockwise respectively anti-
clockwise until a racing speed of 5800-6000 rpm is reached
and the engine runs smoothly.
Correctly adjusted carburetor
When the carburetor is correctly adjusted the machine will
accelerate without hesitation and burble a little at maximum
speed. If the low speed jet L is set too lean it may cause
starting difficulties and poor acceleration.
If the high speed jet H is set too lean it will result in less power,
less performance, poor acceleration and/or damage to the
engine.
If both the L and H jets are set too rich it will results in
acceleration problems or too low a working speed.
L
H
T