Carburetor adjustment
Basic setting:
adjusting needle (L) for low revolutions range 1 turn and 45 min
adjusting needle (H) for high revolutions range 1 turn and 10 min
(the values are derived from the position of clock-hands; the starting point is needle fully
screwed in)
The new engine comes adjusted to the basic setting. This setting should be kept during running
the engine in!
Caution! Never tight the adjusting needles by force. You can damage the touching flats for the
needles. In this way damaged parts cause the carburetor is not possible to adjust and it is
necessary to exchange new carburetor.
After the engine has been run in, adjust it following the instructions below:
- start the engine and warm it up
- let the engine run at idle speed for approx. 5 seconds
If the engine starts to run backwards do not open the throttle - stop the engine immediately!
Otherwise the engine can be damaged!
Step I
Accelerate to 2/3 of the throttle range within approx. 1 sec (faster acceleration).
Repeat three times – if the engine accelerates quickly and without a hiccup go to Step III. If
acceleration is not smooth go on to Step II.
Step II
Faulty acceleration with hiccups and a tendency to cut out is usually attributable to a
poor fuel mixture in the medium-revolutions range. Stop the engine and recheck the fuel feed
(the hose-pipe must not be pinched or broken; if fitted, check also the fuel filter permeability).
Restart the engine and test acceleration again. If problems persist adjust the carburetor. Open
the adjusting needle L by 5 min and retest acceleration. If acceleration is smooth, open the
needle by another 3-5 min - this should be done because the needle was previously set at a
boundary value; if atmospheric conditions changed during flight, the problems might recur.
If the engine still has bad acceleration, open the needle by 10 min. If the engine’s
operation does not improve afterwards, stop it and check the basic setting. Set the adjusting
needle L at 1 turn and 50 min and the adjusting needle H at 1 turn and 10 min. Restart the
engine again and test acceleration. If the engine runs correctly go to Step III. If engine does not
accelerate properly, open the needle by another 10 min. If it does not accelerate, the defect
supposed to be elsewhere than in incorrect adjustment. In this case go to the section on
problem solving.
Step III
If the engine accelerates correctly, according to the above test, set it at idle speed and
accelerate to full speed. Repeat twice more. If the engine functions correctly, go to Step IV. If
it cuts out, open the L needle by 5-10 min more.
If the engine does not respond to acceleration fast enough keep closing the L needle
until the engine starts to cut out in response to gas. At that point reopen the L nozzle by 5-10
min.
Step IV
If the engine reacts correctly set it at full speed. If revolutions do not drop, the engine
has been adjusted successfully. If revolutions seem to drop, open the adjusting needle H by
approx. 5-10 min.
Caution!!! The engine must be stopped while you adjust the carburetor in order to prevent
injury by the propeller.
Caution!!! Never close the choke valve completely when the engine is operating!
The choke valve is set to allow minimum air flow only when fully closed, which could cause
damage to the intake reed valve.
Choke lever
Adjusting needle (L)
Adjusting needle (H)
Crankcase pressure inlet
Air pressure inlet
Fuel inlet
Throttle lever
