The Portuguese tuning specialists, Top Racing, are a symbol of high quality scooter components. Due to Advanced production techniques, and over 50 years of experience many European brands entrust their tuning to Top Racing. The relatively simple installation of The Top Racing transmission is another reason to look no further than the Portuguese brand. To increase performance and speed, you need more power and also a longer gear. Since most vehicles are factory-fitted with a very short gear, you should assemble a longer gear to protect the engine from over-revving and can use more speed. Top Racing transmissions are pre-pressed and ready for assembly. Simply exchange with the original parts and youâre done!. Not really suitable for 50cc cylinders. Top Racing factory specification: Ratio 13/39 18% longer than the original. The primary shaft is supported in variator cover.