How to change a main jet

This is the appropiate procedure to change a main jet without spilling fuel and refilling of the float chamber for an immediately re-start of the engine.

Main Jet

The following procedure can be applied for:

★ 125 Micro MAX

★ 125 Mini MAX

★ 125 Junior MAX

★ 125 MAX

★ 125 MAX DD2


  • Loosen the 2 crews of the intake flange and carburettor socket.

  • Rotax jetting
  • Connect a syringe (60 ml) with the left hole of the venting tube.

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  • Turn the carburettor towards the seat in horizontal position.

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  • In case a big seat is mounted, it might be necessary to remove the carburettor cap with the carburettor slide to be able to turn the carburettor in horizontal position.

  • Pull on the syringe and suck the fuel of the float chamber into the syringe.

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  • Remove the carburettor plug screw, change the main jet and fit the carburettor plug screw again.

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  • Turn the carburettor in upright position and tighten the two crews of the intake flange and carburettor socket.

  • If the carburettor cap and carburettor slide have been removed, they have to be mounted again.

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  • Re-fill the float chamber by pressing the fuel in the syringe into the float chamber.

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  • Ignition ON/OFF switch in position ON and press the start button – the engine will start immediately as the float chamber is already filled with fuel.