Sachs SA 280A Repair Instructions

C._
Carburettor
The type of carburettor, the jet size and the jet adjustment are determine d by means
of tests in the factory. The adjustment determined in this way gives the best results,
and it is therefore not a dvisable to alter it.
No alteration of the carbure tt or setting should be made as long as the engine turn s
over quietly and smoothly when idling, accelerates steadily when t he throttle is
opened, and gives its full output at full revs without choking. If the engine pounds or
runs un even ly, or the exhaust gas is black, the mixture is too rich. Repea ted spitting or
· coughing, or backfiring with a blue flame stabbing from the carburettor co upl ed with
difficult starting, indicates that the mixture is too weak.
When running with the correct carburettor adjustmen t, a cl e an air filter and a suitable
sparking plug with the correct thermal value, the insula tor af the sparking plug should
be brown in colour. Sooty or we t plugs indicate rich mixture, whereas white insulator
points to the mixture being too weak .
Special care should be taken to ensure that the car bur ettor setting is n ever too low,
as at low throttl e insufficient lubricant will be conveyed to the moving parts of the
e
ngine. With a two-stroke engine the carbur e ttor setting should always be sufficient
to provide adequate lubrication.
Correct carburettor se ttings will help to ensure economic and trouble - free running of
the engine.
Adjusting the carburettor for special climatic conditions
When using the engine at al titudes above 1000 metres (3280 ft.), adjustments of the
carburettor setting will be required . As t he air density is reduced at high altitudes ,
the supply of gasoline to the ca rb ur ettor should be rest r icted by changing the main jet.
Starting
On Tillotson diaphragm carburettors the choke is incorporated in t he carburettor
itself.
The choke sho uld be used to facilitate starting from cold. It should not be us ed for
starting when the engine is warm and it should be partially or fully closed only for
s tartin g the cold e ngin e.
Wh en the choke is cl osed, a high er vacuum is caused in the mix ing chamber, so that a
richer fuel/a ir mixture is obtained. Once the e ngine has started, the choke shou ld be
sl
owly opened.
The Tillotson diaphragm ca rb urettor can function in any position and has two dia -
phragms (the HD-7 A type and the HD-13 A type have three diaphragms ): a control
diaphragm for proportion i ng t he fuel feed to the eng ine and a pump diaphragm
(HD-7 A and HD-13 A have two pump diaphragms) for draw ing the fue l from the tank.
Carburettor adjustment
The Tillot so n carburettor is the first carb ur ett or us ed for SACHS e ngin es which has ad -
justable j ets . If engine troubles occur and the jets have to be readjusted , the following
points should be noted:
1. To adjus t the carburetto r correctly for maximum ou tpu t (full load), the eng ine
shou ld be thoroughly warmed up .
2.
With adj us table jet s, car e sho uld be taken not to use too lean a fuel/ air mixture
(see also page 41 ).
3.
The adjusti ng screws for the jets must nev er be screwed to o tightly to the right
(i . e. clos ed) in the jet sea t, as this will deform the sea t.
4. T
he ma in jet is marked "H" and the idling j et is marked "L" on the carbur et tor
housing.
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Sachs SA 280A Specifications

General

Brand	Sachs
Model	SA 280A
Category	Engine
Language	English