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TKART magazine Under Review | The DELLORTO PHBG 18 carburetor of the MINI
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25 November 2021

The PHBG 18 BS carburetor version without holes has been CIK-FIA approved since 2012 with approval number 054-CA-55-ER01 and is used both in some single-brand trophies such as the MINI ROK and in the MINI classes in various national and international competitions.


Carburetors are divided into two distinct categories: diaphragm and bowl (also called "needle"). 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 PHBG 18 has a cylindrical zamak valve which opens and closes the diffuser duct depending on the position of the accelerator.


The PHBG 18 is made of aluminium with a die-casting process. The raw piece is subsequently machined with numerically controlled CNC machines in some areas such as the threads of the float valve needle, atomizer and tray holes. Therefore, the external part of the carburettor body is not machined but only subjected to a shot blasting process.

18 mm

The PHBG is supplied with an 18 mm diffuser for kart use.

Sending the right air/petrol mixture to the engine combustion chamber is an indispensable procedure for achieving the desired performance and reliability of your kart, in which the carburetor plays a fundamental role. Thus, after having analysed the history and characteristics of the king of racing carburetors, the VHSH 30, and of the prince of carburetors used in the ROTAX single-brand classes, the VHSB 34, in our "Under Examination" section, we decided to focus our attention on the PHBG 18, the most popular float/needle carburetor in the MINI classes in national and international championships and single-brand trophies such as the MINI ROK.

The DELLORTO PHBG 18 is a bowl/needle carburetor developed several decades ago for motorcycle use but which, over the years, has been successfully adapted to various other uses, especially in the aftermarket, where it has been used to replace the original carburetors of common street scooters. Available with a range of diffusers from 15 to 21 mm, the DELLORTO PHBG can be considered to all intents and purposes a scaled-down copy of VHSH, VHSB, PHBH and PHBL carburettors. In fact, similar to the latter, and despite its compact size, the PHBG is a complete carburettor that independently has the idle, progression and maximum circuits in addition to the other interchangeable elements such as the atomizer, conical needle, fuel valve, fuel valve screw and mixture screw.
Its versatility, ease of fine tuning, maintenance and the numerous possible adjustments led to the DELLORTO PHBG with 18 diffusers being used as a carburetor in the MINI classes in national, international championships and single-brand trophies. DELLORTO SHA automatic carburettors with 14 and 12 mm diffusers were used as long as it was mandatory, in Italy, to use the Comer engine (derived from engines for lawnmowers) in the MINI and BABY classes. However, when the MINI classes moved to more structured and more performing water-cooled or air-cooled 60 cc engines, it was decided to use the PHBG 18 which allowed more adjustments and greatly increased the performance range. In the MICRO class with 50 cc engines, on the other hand, the DELLORTO SHA was replaced by the PHBN carburetor with a 14-inch circular diffuser, also equipped with all the circuits.
The DELLORTO PHBG 18 is made of aluminium alloy using a die-casting process. Aluminium is a metal material that, thanks to a low melting point and high fluidity, allows the manufacture of components with tolerances very close to those determined during the design phase, but not only that: the metal alloy used to produce DELLORTO PHBG lends itself well to mechanical machining subsequent to die casting and ensures that the final product has significant physical-chemical characteristics such as resistance to wear and corrosion, as well as adequate hardness.
Above, the PHBG 18 and all of its interchangeable components with which you can adjust the carburetion: the [1] cylindrical valve, [2] needle, [3] atomizer, [4] the main float valve needle and [5] the off idle circuit. Below, the different models of DELLORTO carburettors used for karts. From left: SHA 14, PHBN 14 (used in Micro classes), PHBG 18 (MINI classes), VHSH 30 (KZ and single-speed classes of some single-brands, for example ROK) and VHSB 34 (single-brand ROTAX).
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The last substantial change that dates back to 3 years ago was the introduction of this valve cover with plastic ring nut instead of the classic configuration with 4 screws. In this way, thanks to faster access to the valve-needle, maintenance and tuning of the carburetor was made easier.
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The PHBG 18 continues to undergo numerous durability tests to evaluate the wear of moving parts and to optimise the characteristics and performance of the product.
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