12.3 Engine components
Carburettor adjustment
The carburettor is adjusted at the factory for
optimum performance. Subject to the place of use
(mountains, low-lying areas), the average idling
speed given in the specification can be adjusted
as follows, via the idling end-stop screw "T" (the
use of a rev counter is recommended):
If the idling speed is too high, turn the idling
end-stop screw "T" anti-clockwise.
If the idling speed is too low (engine stops)
turn the idling end-stop screw "T" clockwise
until the engine runs smoothly.
If the idling speed cannot be set correctly with the
idling end-stop screw "T", request an authorised
service centre to tune the carburettor.
The adjusting screws for the idling mixture "L"
and the full-load mixture "H" must only be
adjusted by an authorised workshop.
Operating and maintenance instructions
Information about the spark plug
Check the spark plug regularly
after 50 hours of operation.
Removing the spark plug:
Press the top tab of the spark plug cover (16) down
(a), push back (b) and remove.
Remove the spark plug cap below this.
Remove spark plug using the combination spanner
and dry thoroughly.
When the spark plug has been removed or the
ignition cable has been pulled out of the plug cap, the
engine must not be moved. There is a risk of fire
through sparks.
Checking the spark plug:
Clean spark plug with a dry cloth and check
electrodes. There must not be any dirt between the
electrodes. Brush dirt out with a thin paintbrush if
necessary.
If the electrodes have been heavily worn away,
replace the spark plug immediately – otherwise
after 100 hours run.
The correct electrode gap is 0.5 mm. If the
electrodes are bent and the electrode gap is
incorrect, replace the spark plug.
Before starting work, check ignition cable for
perfect connection and insulation.
The permissible spark plug (interference-free, energy
value 240) is available under the following
description:
BOSCH USR 4 AC
Fitting the spark plug:
Refit the spark plug and tighten using the
combination spanner (recommended torque if
using a torque spanner 10 Nm).
Always push the spark plug cap firmly onto the
spark plug.
Position spark plug cover (16) on casing and push
on until it clicks back into place.
ENGLISH 15