Sounds like it was not oiled before start up. It is splash feed
oil. If you do not change the rpm around during the brake in the
oil may not be getting kicked around enough to lube the gear. We use motor honey or the like on the cam gear since it sticks like glue and will take a fair amount of use before it starts to break down. If it ran for 10 min it should run for more. If it is blowing black that is a fuel problem. Check the float level.