Minimoto manufacturers include Polini, GRC, Pasini, Stamas, ZPF, DM, GEM, Vitorazi/ATM and Blata. All are Italian, except for GEM (British) and Blata (Czechoslovakian).
The bikes are also available in 2 sizes, mini and midi. There is no official distinction between the 2, but midis are normally around 10% bigger than minis. This means that midis tend to be a bit more comfortable to ride than minis, but some people find that minis handle better due to their smaller size.
All of the manufacturers use a Polini engine, with the execption of Blata who use an industrial engine on their 2.5 models (2.5 is the kilowatt rating of the engine, it's about 3.4 horsepower), and their own engine on their Elite and B1 Origami models. Pasini also produce a 4 stroke model aswell as Polini engined bikes. The Italian bikes tend to be the most popular with racers, although Blata is very popular in the USA.
The race minimotos compete in different classes, depending on the engine power output. The main classes are 4.2, Production, and Supers. There can also be sub-class in each of these, such as Lightweights, Heavyweights, Juniors, and Seniors, but this is up to the race organisers.
The 4.2 class relates to the Horse Power output, and is exactly what it says, all the bikes are limited to 4.2 horsepower, with no internal, carb, or exhaust modifications allowed. This creates a level playing field for all the riders, so winning races purely comes down to rider skill.
Production class bikes produce around 8 or 9 horsepower. The class rules allow for exhaust tuning, but no internal or carb modifications. Production class racing is the most popular class,
In the MiniMotos Supers class, just about anything goes! 50cc engines, porting, bigger carbs, and power output of anything up to 15 horsepower. Only the exceptionally skilled and 'brave' need apply here.
There currently isn't a racing class for MiniMoto Blata 2.5 bikes, although there is talk of one starting soon. The success of this class will depend entirely on rider turn out at the races. It has been tried before, and a grand total of 1(!) rider showed up (I don't know if he got the trophy or not...). There are probably more Blatas sold than any other make of minimoto, but it seems most end up being used as car park toys. So, if you've got one, get down to your local track on a practice day and make your presence felt!
The MiniMoto Polini 2 stroke is a pretty simple single cylinder, all aluminium lump. Being a 2 stroke, high revs and silly power bands are the order of the day. The engine is pretty reliable, but reliability does suffer slightly as you increase the power output. Engines are generally rebuilt once a season. There are a number of people who will do this for you if you're not too handy with the spanners, and prices start at £50 plus parts.
If you take basic care of the MiniMoto engine, it should give you no trouble. Warm it up before racing, use a good quality 2 stroke oil, and mix it at the right ratio (40:1 when running in, 50:1 for normal use).
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