oh boy. My dad is being damn technical for once. He is all about the fact that Yamaha worked to reduce rotating mass on his viper and the Hauck Speed Sheave weighs 1oz. yes 1oz. more than the stock sheave. The sheave is one of the plates on the secondary clutch. The Hauck one lets the belt ride different for more top end speed. He went to the post office and had them weigh the two for him. The stock one is 1lbs. and 15oz. the hauck one is an even 2lbs. He is upset about it. He was even considering sending the hauck one to school with me so I could turn it down on the lathe in metal working!