Selection Of The Transmission Ratio - BRP Rotax 125 MAX evo Installation Instructions And Operators Manual

Operator's Manual ROTAX 125 MAX evo, Junior MAX evo, Mini MAX evo, Micro MAX evo
¿ Note:
In a disassembled carburetor, the position of the jet needle (pos. 3) can be
changed. The standard position of the jet needle is 'position 2'. If the clip (pos. 4) is
set in 'position 1', the full mixture in part and full-load will 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.
Æ
Remove the hex. screw (pos. 34) and gasket ring (pos. 33).
Æ
Pull out the fuel filter (pos. 32) and clean the filter and fuel inlet.
Æ
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
screwing in the adjustment screw, the air-fuel mixture will become richer at idling
and by screwing out the screw, the air-fuel mixture will become leaner at idling. The
default setting of the adjustment screw are two full turns and one quarter of a turn (2
¼) from inside to outside.
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 rpm.
Transmission ratio 12/72=6
Circumference of rear tire 0.85 m
Vehicle speed = 13000 x 60 : 6 x 0.85 : 1000 = 110.5 km/h
Rotational speed 13000 rpm.
Transmission ratio 12/82=6.5
Circumference of rear tire 0.85 m
Vehicle speed = 13000 x 60 : 6.5 x 0.85 : 1000 = 102 km/h
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