Some claim that the Rotax Kart is the most cost-effective engine in kart racing. The original plan for the Rotax was to build a Touch and Go engine that made karting more affordable but also keeping high speeds.
A "touch and go" engine, also known as TaG, is basically an engine with an electric button start. Here is what Rotax says about their engine:
"Rotax Max is more than a karting class based around a spec engine, it is the embodiment of a return to the art of racing. In a sport that has always been a combination of science and art, these sealed engines have minimized the role of science by combining maximum performance with 50 hours of running time backed by a 6 month warranty."
What this means is you can likely run one of these engines for a couple years before needing a rebuild where other engines may need to be rebuilt every 10-15 races, or twice a year.
A Rotax RM1 Kart
Well, the Rotax was originally just the engine spec, but they have come out with a total kart package called the RM1. Looks like your typical sprinter, a neat thing with this is that the engine and gearbox are all enclosed and there is no chain as the gearbox is situated directly on the axel.
125 MAX "base" configuration:
125 Junior MAX configuration:
125 Mini MAX engine configuration:
125 Micro MAX engine configuration:
125 MAX DD2 engine configuration:
The Rotax Kart and its variations are very popular and fun to drive. Some say the competition from other TaG engine makers, "clones" if you will, are going to make the Rotax become less popular. But we'll see, as of now it's doing well.