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TKART magazine Under Review | TM Racing KZ-R1: the 2019 World Champion Kart shifter engine
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22 January 2020
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2-stroke engine like most kart engines on the market. 4-stroke engines are still a small niche

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125 cc

In karting, gearbox engines have always been 125 cc.

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The usual one, push-start with manually controlled clutch and start in second gear.

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There are two "big families" of engines for karting: single speed and gear. The KZ-R1 is 6-speed.

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KZ 2019-2021

It is the shifter KZ, valid from 2019 to 2021.

The KZ-R1 engine is the new TM Racing’s “weapon” dedicated to the gearbox category, introduced during the 2019-2021 homologation season. Compared to its multi-titled KZ-10C predecessor, this enhanced model has numerous revolutionary changes and refinements which modernizes an already award-winning design, proving once more TM Racing’s ability to remain firmly at the top of this category.

The KZ-R1 analyzed in this article is in the special Red Titan Edition, designed exactly to celebrate the victory of the KZ World Championship conquered by the Dutch driver Marijn Kremers of Birel ART at the South Garda Karting Circuit in Lonato, Italy. However, the aesthetic details that characterize it, such as the anodized aluminum engine plating and the black cylinder head are only the appetizers compared to the numerous new features hidden inside: a long series of improvements designed to increase the reliability and functionality of an engine which, at first glance, is more compact and highly indorsed by the TM technicians, as being much lighter. In this sense, the change that most immediately catches the eye is the reduction of the inter-axis between the various shafts, in particular those between the crankshaft and the gearboxes primary shaft, which is responsible for much of the reduction in size of the entire engine as a whole making it more compact.
More compact dimensions for the KZ-R1 than the previous KZ-10C model
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More compact dimensions for the KZ-R1 than the previous KZ-10C model
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The reduced body size is the result of a series of improvements whose stated goal, however, was not the weight reduction
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The Red Titan Edition of the KZ-R1 is embellished with red features, with the head and the clutch side crankcase cover done in black
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To ensure that the reduction of the primary wheelbase did not create additional problems, the engineers also worked on the dimensions of the cooling circuit and, more specifically, on the section where the fluid goes through once it enters the engine, located between the crankcase and the transmission assembly. Here, the shape of the conduit near the fluid input and output point has been revised to compensate for the narrowing that has been created, where the walls of the gearbox and those of the crank chamber almost touch each other. The fluid, as it flows through this gap, must attempt to transmit as little heat as possible, otherwise there is the risk that the mixture will heat up too much before entering the combustion chamber. For the same reason, the lower part of this amount, at the entry point of the fluid, is now exposed more to the airflow, as this is seen by opening the crankcase.
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