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Tkart magazine

The Expert Advices | Used DELLORTO VHSH 30 carburettor: what to check before going onto a track (and while you are on it)

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29 April 2021

You have to be very careful when buying an entire used kart. Although for some kart components it is easy to understand the set-up and the general state of wear at first sight - the chassis, for example - for others - the carburetor, to name one - it becomes more difficult with just a glance to understand if a different setup is necessary for it to function correctly in regard to its engine or whether it needs a lot of maintenance work to be perfectly efficient again. Furthermore, the point is that if you make a mistake, always remaining in the context of the above-mentioned examples, with the setup of the chassis, at most what you risk is not to have fun driving or to badly consume - perhaps even irreparably damage - tyres. Conversely, if the carburetor setup is wrong, the problems can be very different and have much more significant results on the kart and on the costs.

The carburetor is one of the mechanical parts that most affect the performance and reliability of a kart. If on the one hand the correct carburetion allows the engine potential to be exploited to the maximum, on the other hand a wrong calibration of the removable parts (float valve needles, nozzles, float, etc.) can lead to disastrous results, even seizure, if carburetion is with an air/fuel mixture that is too lean (little fuel). But how do you choose a used carburetor? How can its condition be determined? And what precautions should you take to avoid unpleasant inconveniences? We discussed the topic with Giuseppe Riva, a technician in the DELLORTO research and development laboratories, who answered all our questions regarding one of the most popular carburetors in the karting world, the VHSH 30 used in the main classes, international shifters (KZ, KZ2, etc.) and on the engines of some single-brands (the ROK by Vortex, for example, the ROK GP Junior and Senior, as well as in the ROK Shifter).

N.B. Before reading this article and to understand it better, the editorial staff recommends reading the article "Under review, the DELLORTO VHSH 30 carburettor".

The carburetor is one of the mechanical parts that most affect the reliability of a kart. Incorrect calibration of the removable parts can lead to disastrous results, even seizure

1 What is the first thing to check when buying a used carburetor?

The needle/float carburettor is particularly sensitive to different modifications and, given the many adjustment possibilities, preparation and competence in the choice of calibration is a rquirement. So, basically the first thing you need to do when buying a second-hand bowl/needle carburetor is to check that all the elements it is composed of are in line with a standard calibration table. In fact, there are standard setups communicated directly by manufacturers that allow you to have a good starting point for calibrating it properly. Precisely these “factory settings” offer a sort of lifeline when you buy a used product: this is the starting point, the certainty of having reliable settings, and then you can proceed with the fine tuning. This is why the carburetor must be dismantled and all the removable elements (which can be changed/replaced) need to be checked, including: the pulverizer, the conical needle, the max float valve needle, the off-idle float valve needle, the emulsifier of the off-idle circuit, the float. and the fuel inlet valve. After checking the components inside the used carburetor, it is advisable to always replace the petrol inlet housing and the fuel inlet needle. In fact, these two components ensure fuel sealing and its constant level inside the tank, fundamental conditions for correct and safe operation of the carburetor.

2 The DELLORTO VHSH 30 is a carburetor used by several manufacturers. Can the standard calibration of components supplied by DELLORTO be adapted to any engine?

The versatility of the VHSH 30 means the carburetor can be used for different engines. Precisely for this reason - and because of the number of possible adjustments - it could be the case that your VHSH 30 carburettor, after having been returned to the factory standard calibration, does not have the correct setting for the engine it is combined with. In fact, engine manufacturers buy standard carburetors with standard setups from DELLORTO, but before selling them in combination with their engines, they adjust them according to the strong points and performance of the engines. This is why it is always good to ask the engine manufacturer whether the standard calibrations are suitable. If in doubt, or if you cannot find this information, for the first use we recommend adopting a careful approach with a richer mixture, increasing the max float valve needle and the off-idle float valve needle and raising the conical needle by a notch, compared to the indications of the standard settings, thereby avoiding seizure problems.

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