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TKART magazine How To | How the mixture throttle valve works in KZ karts
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Gianluca Covini
22 October 2021
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The throttle valve was introduced in the karting world by motor coach Patrick Savard in the early 2000s. In the present day it is an accessory used by many professional drivers, who enter the track with very high carburetion, in search of the limit. In fact, using it makes it possible to partially "enrich" the carburetion while driving (an activity that is otherwise impossible to do with float carburetors).
It can be mounted on the steering wheel of KZ karts that have a float carburetor, but how does it work and what exactly is it for? In this article we go into more detail on the logic of operation, tips for installation and advice for using this accessory, whose real usefulness is not known by many.
In karts with a float carburettor and relative petrol pump [A], the “standard” operation is as follows. The piston in the engine moves down and in so doing pushes petrol from the pump to the carburetor. Each time this happens, some of the petrol is sent from the pump to the carburetor [A1], while the quantity in excess of that needed for setting the carburetor is carried, through another tube, towards the tank [A2], so as to become usable in subsequent engine operating cycles. [B] When the valve is introduced, [B1] mounted on the section of the tube that carries the mixture back to the tank, this, if “closed”, allows the flow to be reduced. Following this choking, an increase in fuel pressure is generated on the petrol inlet housing in the carburetor, triggering a rise in the level inside the tank, causing a consequent forced enrichment of the carburetion. By turning the valve, it is therefore possible to precisely change the fuel level in the carburetor bowl, modifying the carburation in a timely and controlled manner. [C] By turning clockwise, the throttling is increased and consequently the carburetion is enriched. Turning counter-clockwise, of course, returns to the original carburetion setting, which is "leaner".
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