Cheap displacement kit for air-cooled Yamaha 125cc 4-T engines. With the additional 25cc you can tickle the one or other horsepower out of the engine. However, a significant change is noticeable through the enlarged bore, which has a direct improving effect on the torque of the engine.
The original cylinder head can still be used.
The installation of the cylinder is simple in principle. However, when removing the timing chain, care must be taken to ensure that the timing of the motor is not changed.