ROTAX 125 MAX evo, Junior MAX evo, Mini MAX evo, Micro MAX evo
become slightly leaner. If the clip (pos. 4) is set into ‘position 5’, the fuel mixture will
become slightly richer in the part and full-load range.
Note: The fuel filter (pos. 32) is located below the fuel inlet on the carburetor, preventing
contamination from entering the carburetor which could impair operation of the
carburetor.
Attention: The fuel filter (pos. 32) must be inspected periodically and cleaned as required.
Remove the hex. screw (pos. 34) and gasket ring (pos. 33).
Pull out the fuel filter (pos. 32) and clean the filter and fuel inlet.
Refit the fuel filter (pos. 32), the gasket ring (pos. 33) and hex. screw (pos. 34).
Note: When trying to start the engine it will take a few seconds for the fuel pump to fill the
float chamber and for the engine to start.
Note: With the adjustment screw (pos. 36), the idle speed of the engine can be adjusted.
By turning in the adjustment screw (pos. 36) the idle speed increases and by turning
out the screw (pos. 36) the idle speed will be reduced.
Note: With the adjustment screw (pos. 31), the fuel mixture formation can be adjusted. By
turning in the adjustment screw, the air-fuel mixture will become richer at idling and
by turning out the screw, the air-fuel mixture will become leaner at idling.
4.2. Selection of the transmission ratio
The transmission ratio (between chain pinion on the engine and chain sprocket on the rear axle of
the kart) has an essential influence on the achievable lap time.
The routing (fluent or non-fluent) and the conditions (high or low tire grip) of the track require a
certain transmission ratio to ensure an optimal lap time.
A longer transmission ratio (e.g. 12/72=6) theoretically results at every rotational speed of the
engine in a higher speed of the vehicle, but also in a higher driving resistance than with a shorter
transmission ratio (e.g. 12/78=6,5).
Calculation Example:
Rotational speed 13000 r.p.m.
Transmission ratio 12/72=6
Circumference of rear tyre 0,85 m
Vehicle speed = 13000 x 60 : 6 x 0,85 : 1000 = 110,5 km/h
Rotational speed 13000 r.p.m.
Transmission ratio 12/82=6,5
Circumference of rear tyre 0,85 m
Vehicle speed = 13000 x 60 : 6,5 x 0,85 : 1000 = 102 km/h
In principle, the transmission ratio should be chosen so that the engine is mainly operated in a
speed range at which the engine performance is well above the driving resistance.
The following chart (125 MAX evo) shows that the difference between the engine performance and
the driving resistance constantly increases at a speed range from 5000 to
9000 r.p.m., remains the same at a speed range from 9000 to 11500 r.p.m. and decreases again at
a speed about 11500 r.p.m. onwards.
Seite/page 79/98
Ausgabe/Edition 11/2014
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