considering harley uses something similiar to the cog belts on their drive wheel says something of the toughness of the belts. like others say, tension is critical. i had one belt adjusted too tight and it snapped, what happened is i adjusted it cold, when things heat up the distance is greater between parts and the belt snapped or seperated. i have adjusted them too loose also, like on the
oil pump. sounded like a loose tappet and would go away when things warmed up, actually the tooth was skipping. belts are 15-20 plus shipping, and i'm not talking about the wide ones pictured above. my preference would be v belts or the ribbed belts used in serpentine applications. i believe the ribbed belts are supposed to use less hp.