I Sir . 2years ago I changed my Wheel shaft bearing, by new one from Piaggio. I started to ear some gear sound inside the Gear case. I decided to change all bearing inside gear case cover and block motor housing. I reisntall all and it was looking same sound . I remark oil was coming black, and I started to find some bright part´s of metal inside oil. I changed many times per year but noting good happend, continue to find part´s of metal and continue to coming black after fews hours of running. I am started to coming confuse about this problem because I visited Vespa dealer in Quebec city canada and they found nothing after dismantle all gears and evrything. . !!!. Thanks to let inform Francois Matte Canada