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 you’re done!. Not really suitable for 50cc cylinders. For Piaggio engined scooters with original intermediate shaft with 14 teeth. Top Racing factory specification. Ratio 14/42-14 Increase of 19% Tuned transmissions generally feature straight toothing, in order to reduce friction. This leads to slightly more noise, but is harmless.. Suitable for: Cagiva Progress Derbi Atlantis 50 LC Derbi Engine Derbi Padlock Derbi Predator 50 Air Cooled Derbi Predator 50 Liquid Cooled