MVVS 50 IRS - Manual (Page 3)

Carburetor Adjustment
Basic setting: (The values are derived from the position of clock-hands)
adjusting needle (L) for low revolutions range 2 turns and 0 min
adjusting needle (H) for high revolutions range 1 turn and 30 min
The new engine comes adjusted to the basic setting. This setting should be kept during
running the engine in!
Crankcase pressure inlet
Choke lever
Adjusting needle (H)
Adjusting needle (L)
Throttle lever
Throttle stop screw
Caution! Never over-tighten adjusting needles by force, because it can cause damage to
the needles and carburetor. Carburetors worn like this can not be adjusted and will need
to be changed for a new one.
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 hesitation, go to Step
III. If acceleration is not smooth go on to Step II.
Step II
Faulty acceleration with hesitation 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 (60 degree).
If the engine’s operation does not improve afterwards, stop it and check the basic setting.
Set the adjusting needle L at 2 turns and the adjusting needle H at 1 turn and 30 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 problem is likely to be caused something other than an 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 from fuel starvation. 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.