Hi, there is a big bore kit available that turns it into a 53cc, dont expect much added speed but there will be more torque definetely. This engine is commonly used in goped's, midi moto's, petrol scooters, mini choppers, mini harleys, some older pocket bikes, petrol skateboards etc.
You can get expansion chamber pipes for it, air filter and velocity stack sets, boost bottle, even nitrous!