A failure analysis has been carried out on a riveted half pulley mounted on the CVT system of the new Piaggio 850cc twin engine. First of all, different design variants have been analysed with simplified models, in order to single out the one with the best performance. The best configuration has then been re-analysed with a more detailed model, including the stress state induced by the riveting process, which has been simulated with a separate model. The working conditions corresponding to Piaggio standard endurance cycle have been used to estimate the fatigue damage withstood by the component. Finally, the critical working condition has been singled out and the corresponding stress state has been compared with the one arising during Piaggio standard bench test for the component under examination.