Jonsered 70C 用户手册

30 – 

English

Your Jonsered product has been designed and manufactured 
to specifications that reduce harmful exhaust fumes.

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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.

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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.

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The carburettor has three adjustment controls: 

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L = Low speed jet

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H = High speed jet

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T = Idle adjustment screw

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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.

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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.

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

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.

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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.

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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.

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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.

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.

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.

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.