30 YEARS OF FLOAT BOWL CARBURETTORS, WITH 9 MODELS AND 3 SOLUTIONS… EXTREME!

The Mikuni Kogyo 35 made of magnesium does not have any identification marks on its body. However, we know that the Mikuni Corporation usually uses the letters VM for its round valve carburettors, with this structure (the letter V stands for round guillotine and M for the type of body that must work vertically and with the guillotine operated directly from the cable) followed by the diameter dimension in millimetres. There are no abbreviations on the body of this carburettor to recognise it with precision. The impression that this model gives, at first glance, is that it is very compact, perhaps a little squat. However, let's not forget that we are dealing with a diameter of 35 mm, much larger than the current ones used in the KZ class. The fact that it has a diameter like this and overall small dimensions is due to the fact that it was made for motorcycling where the dimensions had to be reduced to the bare minimum. It is easy to understand that, in order to maintain a resistant structure, there was little room to go further with the diameter of the duct, because looking at the rear part that is inserted into the intake manifold, we notice how much the thickness of the connection is reduced to a minimum. Its duct has a cylindrical section, with a real diameter of 34.9 mm, and mounts a traditional round valve combined with a yellow plastic ring nut and a starter kit with short clip, less practical than the lever one used today. but still very easy to use and contained in size. We are unable to measure the original external inlet on the intake side since it has been modified and brought to 63 mm, for use strictly without a filter as required at the time in the racing field. This model was made in two versions, a "right" and a "left" to ensure that it worked correctly when cornering, when the bike remained leaning and it was necessary to allow the normal oscillation of the float inside the tank. In fact, the float was connected via the balance wheel laterally with respect to the central axis of the carburettor. The two versions also had different petrol inlets positioned with respect to the intake on the right or left side in such a way as to always remain facing forward.

Thanks to this carburettor, Alessandro Piccini retraces the first years of his career, which began almost for fun (for further information, read "Editorial - Alessandro Piccini: from 40 in karts") "This 35 mm Mikuni Kogyo was an absolutely performing carburettor from all points of view: it allowed a greater range of use than other carburettors popular at the time and had a fairly good delivery response in relation to its short length despite a round and not flat guillotine. The initial diameter was 35 mm, but sometimes it was enlarged, even if the available thickness was really reduced". With the help, and several suggestions, from excellent trainers, Alessandro immediately began to modify this carburettor in various aspects, including, for example, a very important Venturi flange, created on a lathe and then mounted for interference. However, Alessandro tells us that this modification, which we have noticed, is the latest in a long series since "it was very difficult to find the best radii without spending hours on the flowmeter which at the time was not so close at hand, we needed a lot of evidence". In fact the changes, mainly took place due to study, specific knowledge and a lot of experience. If we analyse it carefully, we notice that it has even gone in the opposite direction to what the vast majority of enthusiasts would think: the inlet diameter has even been reduced to 30 mm, with a very precise radius, both in the front and in the one at the rear of the aluminium flange, which however we were unable to measure. This allowed greater stress on the pulverizer (soiled pulverizer), with better performance over the entire range of use of a kart engine.