Rotax » Dellorto Carb

The carb doesn't need too much attention provided the fuel supply is always kept clean preferably with both an in-tank filter and an in-line filter as well.

The main jet needs to be changed to suit the circuit and weather conditions and this is critical for performance.

As well as different main jets  you can use 2 types of needle; K27 or K98 - the K98 has a slightly squarer section meaning that it lets in less fuel at smaller throttle opening. You may also use alterative idle jets and floats but beware they can only be used in fixed combinations:-

With 5.2 gram floats you must use a 30 idle jet and 30 idle tube.

With 3.6 gram floats you must use a 60 idle jet and 60 idle tube.

There are 2 types of carburettor - 8.5 and 12.5 - this refers to the size of the drilling in the venturi directly below the slide. Both types are legal and provide a different bias of power although may not make a huge difference in overall lap times. You can find out what type you have by removing the carb top and slide; you will then find a number stamped in the top of the venturi below where the slide normally sits.

MOJO
TILLOTSON
BRIDGESTONE
DUNLOP
MAXXIS
TKM
ARAI
IAME
DID
HONDA
TILLETT
MIR
TONYKART
ROTAX
RK
SPARCO