MINI 60 CC, THE “SMALL” ENGINE OF THE TM RACING

Max Bernardi

16 July 2018

TYPE
A 2-stroke engine, like the vast majority of the kart’s engines. The 4 T is a small niche

60 cc

DISPLACEMENT
60 cc. It is the displacement which provides power to the chassis used in the Minikart

ELECTRIC

START
Electronic start handled by the driver via a start button.

SINGLE SPEED

TRANSMISSION
There are two of the large categories for kart’s engines: the single-speed and the shifter one. The 60 cc is a single-speed

2020

HOMOLOGATION
The homologation of the 60cc engine by TM Racing is valid from February 2015 to all of 2020

With the 2015 homologation, the TM Racing debut in a category which was new for the company and never managed before: that of the 60 cc engines. Not an easy challenge to create a completely new engine, destined for the most numerous and competitive class in the karting scene. Yet, three years later, the challenge can be confirmed as being decisively won: the 60 cc by TM Racing is the most present product on the starting grid of the most important races. A success that certainly needs to be analyzed in detail!

The first thing to emphasize is that the designing of the 60 cc engine was not at all easy for TM Racing. Being their first engine destined to the 60 Mini, the Italian company from Pesaro (Italy) did not have any prior experience on which to base itself and a radical study had to be implemented. Many bench tests have been executed, for the occasion, departing from a plastic cylinder, with short tests on a cold engine so as not to overheat the material.

As Franco Drudi, the official coach of TM Racing: “The 60cc engine, although it is lower in displacement in comparison to a 125 single-speed or a shifter, is more difficult to design, precisely because of its reduced power”. With only 11 HP available, the smallest of details are what makes the difference: just think that during the tests at the engine stand, TM technicians counted the number of oil sprays on the chain, as this caused a variation of the results. Moving on to the actual analysis, it should be highlighted how the new 60cc head brings back the cooling study of the old TM air-cooled engines with the characteristic fins.

The TM Mini 60 cc is the first TM Racing engine designed for the 60 Mini class

The fins of the head’s rear area are longer than the front ones, this improves the cooling of the engine parts with higher temperatures.

The latter are exactly one of the most complicated parts to obtain in the melting phase, as the machining must be executed by placing innumerable inserts in the correct sequence. It might seem strange, but for TM Racing the 60cc engine results are more complicated and more time consuming to produce, in the melting phase, than a KZ 10 C engine designed for the shifter categories. Still focusing on the head, looking at it from the sprocket side, one notices how the front and rear profiles are different: in the front the fins are lower than the rear ones. This helps in channeling the cold air to the warmer areas of the head (the rear area), where the longer fins help to reduce the temperature. If, instead, one analyzes the head from above, one notices the lack of fins in front of the spark plug: a choice made to channel more cool air onto it. The spark plug area is also the only one where the ring which connects all the fins making them a single body, thus increasing their rigidity, is interrupted. In the past, in the old air-cooled engines, silicone inserts were put between the fins so as to absorb vibrations and avoid their breakage: a trick which is no longer necessary in the new 60 cc by TM Racing.