Raket 95 Owner's Manual - page 22
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22
Raket 95 Manual - English
which you can check by using the same
method as we have previously described.
If you still – despite everything – are not
able to receive fuel then the needle valve
must be stuck and in that case there is
nothing else to do than to continue. The
pump pushes the fuel forward towards the
needle valve, but it cannot open it through
its own force. The needle valve is held
closed by a spring that operates over a le-
ver. The master diaphragm works against
the lever, which we know from the small
rivet in the middle of the diaphragm. One
side of the diaphragm is in contact with
the carburettor’s venturi. When the fuel is
sucked out through the needle valves, the
amount of fuel beneath the diaphragm is
reduced. This in turn applies pressure to
the lever and cancels the spring’s force.
Now the inlet valve can open and more
and more fuel can flow in – the chamber
beneath the diaphragm fills up and the
diaphragm moves outwards. In this way
the spring closes the needle valve and
maintains a relatively constant amount of
fuel in readiness for the needle valves.
Fuel can find its way out of the chamber
to the carburettor’s venturi via the H and
L screws. The channels there are so thin
that the fuel will not normally escape
of its own accord but rather must be
sucked out. The shape and placement
of the channels in the venturi decide the
characteristics of the carburettor. That is
however not something that we shall go
into in any more detail here.
Now we can start with the needle valve.
Take away the pressed metal cap and the
master diaphragm together with its gas-
ket. By loosening the small screw that can
now be reached, the needle valve can be
disassembled. Be careful that the spring
does not come loose! Now you should
check the needle valve itself (nr: 25) to
ensure that its pin is totally even – change
it if you are unsure. Check that the seat-
ing at the bottom of the valve appears to
be even and undamaged. Unfortunately
it can happen that the seating sustains
damage in which case the valve will not
be able to close properly.
When you have checked and cleaned
everything it is time to reassemble the
needle valve with its lever. The spring
should not be deformed (you should
always have a couple available to change
when necessary) and the lever should
not be bent. When you assemble the
valve, the part of the lever that has a
fork that fits onto the master diaphragm’s
rivet should lie exactly at the edge of the
carburettor’s rough surface.
Now you should attach a small air pump
with a manometer (art nr: 5054) to the
fuel nipple on the pump side. Drop a few