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Under Review | The ROTAX DELLORTO VHSB 34 carburetor

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More than approval, in this case it is better to refer to the Rotax regulatory technical file valid since 2015. The DELLORTO VHSB 34 is the carburetor used in all classes of the ROTAX Max Challenge single-brand: from Micro to DD2, passing through Mini, Junior and Senior Max.


The carburetors are divided into two distinct categories: those with a bowl (also called “needle” carburetors) and those with a diaphragm. In this case the air flow is regulated by the opening of the fuel valve while the main petrol inflow depends on the ascent of the conical pin.


The VHSB 34 has a flat valve that opens or closes the diffuser duct depending on the position of the accelerator.


The VHSB 34 is made of aluminium undergoing a die-casting process. The raw piece is subsequently machined with numerically controlled CNC machines on the threads, holes and inlet seats of the float valve needles, nozzle and fuel valve housings.

34 mm

For karting applications, the VHSB is supplied in only one size with a 34 mm diffuser.

The carburetor is one of the main components inside our beloved karts. An essential and fundamental element that regulates the right amount of air/petrol mixture flowing into the combustion chamber. After analysing the operating principle of the float chamber/needle type carburetor in the "Technique" section of our magazine and having dedicated an article in the "Under Examination" - the DELLORTO VHSH 30, one of the most used carburetors in the karting world, we decided to focus our attention on another extremely interesting product that has a completely different construction and application philosophy. It regards the DELLORTO VHSB 34, the carburetor used in all classes/engines of the single-brand Rotax. Let's find out about it.

The DELLORTO VHSB 34 is a float/pin type carburetor invented several decades ago for motorcycle applications, in particular for the Aprilia Sport Production 125 models. Over the years it has been optimised, modified and also intended for karting use, not so much with the goal of achieving ever greater performance, but with the wish to supply a product that is easily manageable in terms of carburetion calibration and very reliable even in high stress conditions. In fact, the DELLORTO VHSB 34 is a carburetor that is very close to being a standard product and its main characteristics such as quality, constancy of operation and production tolerance between the various models perfectly suit the racing philosophy on which the Rotax single-brand trophy is based.


    The 64 mm diameter attachment on the suction side for mounting the air filter fittings.

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    Attachment on the engine side for mounting an elastic with a diameter of 44 mm.

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    The starting device used for starting the kart when cold.

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    The air screw regulates the amount of air that passes into the idle circuit.

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    The idle screw adjusts the stop point of the gas valve, then defines how open the gas valve is when the accelerator is not pressed.

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