In the world of karting, engines, theoretically, should last for the three-year homologation period and then be ready for the scrapyard , sold to hobby drivers or used for training in rentals. But it doesn't always go that way… (by Pierluigi Mancini)
Published: 24 February 2026
Columns: On the technical side
The life of a kart engine, according to regulations, should be 3 years, namely those of homologation. Unlike what sometimes happens with chassis, in the engine sector this almost never occurs: the old one always performs worse than the new one. In many years on the track, I rarely remember old engines going faster than those of new homologation. Not that chassis builders are less skilled than engine builders—quite the opposite—but it is undisputed among everyone that it is easier to find the right path on an engine rather than on a chassis.
The problem is another one: what is the destination of an engine at the end of homologation? Hundreds of thousands of Euros are spent on molds and equipment, plus design and development costs, and everything is thrown into the landfill? No, absolutely not. While chassis have homologation extensions (engines do too, but few use them unless after making substantial modifications especially at the level of the thermal group, crankcase, and crankshaft), for engines it has rightly been observed that it is useless to remake the crankcase mold or the cylinder exterior every time a new model is homologated. Since crankcase internal profiles are now finished by machine, perhaps a detail modification is made to the conchiglia, the machine tools are worked differently, but with today's production numbers, everything is rarely thrown to the scrap heap, unless the engine in question has been a source of embarrassment for the manufacturer.
From KF to OK
The failure of the KF categories had only one precedent in kart history: the ignoble 135 class. All manufacturers developed new engines for the 125 cc single-gear, facing ridiculous sales figures. However, not everything was thrown away. The cylinder and head molds remained the same on different OKs, and in some cases, the starter motor support was simply milled off the crankcase to turn a KF into a potentially winning OK!
Rotax: winning choice
Rotax, when it created the namesake single-make trophy with what is today the Rotax Max Evo, did not develop an engine from scratch. Or at least, it made good use of the experience gained in the motorcycle field. The thermal group, crankshaft, and internal crankcase conformation indeed derived from the 122 engine, used by Aprilia on the bestselling 125 cc RS and RX. The thermal group, in fact, has always stood out for its power and reliability: what reason was there to develop a new component from scratch? Even the motorcycle-derived air filter housing was used on this engine, which, thanks to these smart economies of scale, turned out to be economical yet powerful and reliable.
The problem is another one: what is the destination of an engine at the end of homologation? Hundreds of thousands of Euros are spent on molds and equipment, plus design and development costs, and everything is thrown into the landfill? No, absolutely not. While chassis have homologation extensions (engines do too, but few use them unless after making substantial modifications especially at the level of the thermal group, crankcase, and crankshaft), for engines it has rightly been observed that it is useless to remake the crankcase mold or the cylinder exterior every time a new model is homologated. Since crankcase internal profiles are now finished by machine, perhaps a detail modification is made to the conchiglia, the machine tools are worked differently, but with today's production numbers, everything is rarely thrown to the scrap heap, unless the engine in question has been a source of embarrassment for the manufacturer.
From KF to OK
The failure of the KF categories had only one precedent in kart history: the ignoble 135 class. All manufacturers developed new engines for the 125 cc single-gear, facing ridiculous sales figures. However, not everything was thrown away. The cylinder and head molds remained the same on different OKs, and in some cases, the starter motor support was simply milled off the crankcase to turn a KF into a potentially winning OK!
Rotax: winning choice
Rotax, when it created the namesake single-make trophy with what is today the Rotax Max Evo, did not develop an engine from scratch. Or at least, it made good use of the experience gained in the motorcycle field. The thermal group, crankshaft, and internal crankcase conformation indeed derived from the 122 engine, used by Aprilia on the bestselling 125 cc RS and RX. The thermal group, in fact, has always stood out for its power and reliability: what reason was there to develop a new component from scratch? Even the motorcycle-derived air filter housing was used on this engine, which, thanks to these smart economies of scale, turned out to be economical yet powerful and reliable.
.jpg)
The 'family ties' of the Rotax 125 (which essentially invented the single-make in karting) with motorcycle production, make it one of the most reliable engines ever
(3).jpg)
From Leopard to X30
IAME, when it decided to create a new single-make, focused on developing the 125cc Leopard engine, which was already selling successfully worldwide. In the early 2000s, the TAG ('Touch and Go') category was born, and consequently, IAME developed a powerful and relatively economical engine to offer to its international clientele. The engine proved performant and reliable, so much so that it was used as the starting base for developing the X30 engine. We can say that without the Leopard, there would be no X30 engine as we know it today. But it is also true that the Leopard gave birth to the MRC XTR engine, the 3-transfer port that proved particularly competitive even in KF Junior.
(1).jpeg)
The Leopard, IAME's first true "TAG" engine at the start of the century, can be considered the "dad" of the world-famous X30
And the 100s: what happened to them?
As we have been able to verify, a good product and good equipment live beyond the years of the first homologation. Staying within IAME, the KA100 is an engine developed by the Bergamo-based company for the Australian market and, more specifically, for the single-gear Junior class, then extended to other Senior and Master categories in the USA and several other countries. It is a 100 cc long-stroke engine, bore 48 mm and stroke 54 mm, with reed valve intake and air cooling. Apart from the characteristic dimensions, this KA100 intelligently reuses, according to economies of scale, nothing less than the thermal group and engine crankcase from IAME's 1990s reed valve engines—features that cannot escape an attentive observer with some years of experience. To implement electric starting, an external starter motor support flange bolted to the crankcase was created: an economical and smart solution. There's nothing wrong with reusing what's good in-house, especially considering that, with production costs for molds and equipment widely amortized, these engines end up costing little, being extremely reliable, and offering excellent performance.
As we have been able to verify, a good product and good equipment live beyond the years of the first homologation. Staying within IAME, the KA100 is an engine developed by the Bergamo-based company for the Australian market and, more specifically, for the single-gear Junior class, then extended to other Senior and Master categories in the USA and several other countries. It is a 100 cc long-stroke engine, bore 48 mm and stroke 54 mm, with reed valve intake and air cooling. Apart from the characteristic dimensions, this KA100 intelligently reuses, according to economies of scale, nothing less than the thermal group and engine crankcase from IAME's 1990s reed valve engines—features that cannot escape an attentive observer with some years of experience. To implement electric starting, an external starter motor support flange bolted to the crankcase was created: an economical and smart solution. There's nothing wrong with reusing what's good in-house, especially considering that, with production costs for molds and equipment widely amortized, these engines end up costing little, being extremely reliable, and offering excellent performance.
.jpg)
From IAME's history (here Alonso in 100 ICA on MW-IAME in the 1990s) comes the KA100, an engine very popular today in the USA and Australian markets
-
Positive assessement after the first two races of the season
-
Julia Angelard returns to Valencia for the COTFA round
