125 Open Gearbox
This class is the Open 125 Gearbox class. It is open to the use of motocross 2-stroke engines but by far the popular choice are the Grand Prix engines supplied by Honda (RS125) & Yamaha (TZ125). In this class you are allowed the use of full body kits & wings etc.
Front & rear brakes are compulsory. Leather suits are not compulsory but are highly recommended.
To be successful in this class a competitor must be prepared to get their hands dirty, as these Grand Prix engines require regular maintenance & tuning to make good use of the 50hp they are able to produce.
Running costs are reasonable. It could be said that due to the fact that these engines have only one cylinder that they cost half as much as a twin cylinder 250 International Superkart, i.e. 1 piston & ring, one crankshaft, one set of reed petals etc.
The class weight for the 125 Open Gearbox Superkart is 180kg minimum (kart & driver). Some quite impressive lap times can be achieved in this class. Phillip Island (1:42.7), Sydney Motorsport Park GP circuit (1:37.3) and Wakefield Park (1:01.7).
To get into this class, used karts can be purchased from as cheap as $4000 to $5000. A new Open 125 Superkart can vary in price from $20,000 upwards, depending on your choice of engine, brakes, bodywork, instruments & so on.
Since the inception of the CAMS Australian Superkart Championship, in the 125cc Gearbox Class, nothing has taken a championship away from the Honda RS125 Grand Prix engine.