Vibration and heat-insulated carburettor
Every engine gives off a certain degree of vibration. The
carburettor has a number of moving parts such as the
control valve with its lever and diaphragm and the car-
burettor’s throttle spindles. Their function is affected by
vibration, with the effect growing in proportion to the
mass (weight) of the parts. (Light parts have a greater
ability to follow vibration-induced oscillation than do
heavy parts.)
The carburettor and its moving parts are larger in large
machines, so the K950
and K1250 Active
feature a vibration-
damping element
between the cylinder
and carburettor.
This element also
serves as a heat in-
sulator and prevents
the formation of
vapour in the carbu-
rettor.
Decompression valve
Large engine offers
relatively high resis-
tance at the starter
cord. The decom-
pression valve
solves this problem
in a simple and effi-
cient way.
When starting the machine, the valve is first opened
by pressing the button. When the operator pulls the star-
ter cord, most of the compression pressure exits through
the valve and the starter cord’s
movement is both gentle and
even. As soon as combustion
takes place in the cylinder, the
valve is shut automatically by
the combustion pressure and
the engine operates normally.
Cylinder/piston
The Partner K950 Active and K1250 Active have special-
ly developed air-cooled two-stroke engines running on
unleaded 95-octane petrol. They are lubricated with oil
mixed in the petrol.
There are two
types of flushing
duct - open and
closed. Large two-
stroke engines work
more efficiently with
closed flushing
ducts, which is why
the K950 and
K1250 Active
feature this system.
The cylinder bore is hard-chromed. The piston has two
piston rings, and it has needle bearings at the coupling
with the connecting rod.
The cylinder and piston are made in a way which
ensures ideal dimensions during operation. The piston is
profile-turned and the cylinder is honed for the tempera-
ture — and the accompanying material thermal expan-
sion — which each part of the cylinder and piston expe-
rience during operation. For example, the piston, when
seen from the side, has a somewhat barrel-shaped profi-
le, while the view from above reveals a slightly asymme-
trical oval shape.
This design gives the engine maximum power through
perfect sealing in the cylinder chamber allied to mini-
mum frictional loss against the cylinder wall. However,
this production method is both complex and expensive.
Starter unit
The Dura Starter is a new patent-pending starter unit
designed specifically for the dusty operating conditions
in which cutting machines are used. The Partner K950
Active is the largest machine to feature Dura Starter.
Dura Starter — new dust-excluding design
The principle of the new starter unit is that the pulley is
protected from vibration-induced movement. This makes
it possible to fit a series of seals and a grease-lubricated
bearing.
The spring above the pulley exerts a tensioning force
against the centre screw and acts as a brake on vibra-
tion-induced movement. An O-ring above the spring pre-
vents dust from penetrating into the pulley’s bearing. The
spacer sleeve around the centre screw is the pulley’s
upper bearing point and the entire pulley is journalled in
a slider bearing against the starter casing’s bearing pin.
The space between the pulley and the spring cassette
is shaped like a circular labyrinth, which prevents dust
from moving towards the centre. The spring cassette is
sealed against the
centre with a spring-
loaded sealing lip
lying against the
pulley.
4
Return spring
Sealing lip
Spring
O-ring
Starter cord
Spring cassette
Pulley
Starter casing
Journal bearing
K950 Active
K1250 Active
Open
Closed
