Radne Raket 85, Руководство пользователя

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10
Users Manual
10
How to check the correct opening pressure for the needle
valve.
Connect a small air pump with a manometer to the fuel nipple of
the carburettor. Drop some fuel on the needle valve and pump up
some pressure. At 1.0 kp/cm2 the needle valve shall open – and
you can see that it bubbles around the needle valve. Now reduce
the pressure down to 0,5 kp/cm2. Check with a few more drops of
fuel that the valve is tight – no more bubbles. If the valve is leak-
ing all the time, clean everything again and change to a new valve
and spring.
If the opening and closing pressure don’t match the values given
in the text, you have to change the spring and lever until it is
correct. Finally, take a last check of the main membrane and
the gasket, there is very little that can go wring with these. If the
carburettor is carefully cleaned and you have checked everything
according to the instructions and the H and L needles are OK
– the carburettor works.
The only problem that can remain now is if the engine is very dif-
ficult to start and don’t react on adjustments of the L-needle. Then
there could be dirt under the expansion washer, which is located
under the main membrane. The fuel that passes the L-needle is
also passing a small chamber on its way to the venturi. In very
rare cases this chamber can be blocked. To solve this problem
you have to drill a 2 mm hole in the middle of the washer (3020)
and pry a thin tool into the hole and bend up the washer. Clean
and check all channels to and from the chamber carefully and seal
it with a new washer. To do this, place a new washer in correct
position and expand it with a gentle blow of a small hammer. That
is all, now your carburettor shall be working. Normally this mem-
brane carburettor will give you very few problems, but sometime
you get a carburettor that doesn’t give good results. Then try to
borrow a carburettor that you know works well. If the difference
between the two is big, you have to buy a new carburettor. It is
very difficult to change a band on into a good one.