As an effort to improve performance on 4-Stroke gasoline engine, in addition to redesign and modification techniques, it is also can be done by bore up the piston. The application of bore up on a small CC motor can be done by modify or changing the piston ring, carburetor, inlet and exhaust valve. Changing the capacity of the larger combustion chamber will require more air and fuel supply, so that combustion energy will be even greater. Once the motor power matches the expectation, gearbox replacement is need to distribute the motor power to get a maximum power result. This research uses experimental method, as a way to find cause and effect relationship between several factors that influence each other by comparing 2 condition, that is condition 1 (standard) and condition 2 (aftermarket). The tests conducted were fuel consumption testing, dynotest testing, and acceleration testing to determine the effect of replacing the aftermarket gearbox components on the performance of Yamaha Jupiter motorcycle engine 130 cc. The result obtain were analyzed. As a result, by replacing the aftermarket gearbox components will make motor performance higher and better than using standard gearbox components. With the replacement of this aftermarket gearbox components make greater result of final reduction and less reduction of rpm when switching gear. The result of the test shows that the performance of Yamaha Jupiter motorcycles 130 cc of torque of 16,59 Nm and power of 25,7 HP at 12218-rpm rotation, in terms of fuel consumption testing can travel a distance of 24,91 Km / Liter and on acceleration testing resulting in 8,6 seconds in 201 m distance.