have twin blade walkbehind mower. has 56" drive belt. uses hand control to apply belt pressure. put on new belt and adjusted lever for proper feel. mowed about 1 hr. son mowed again today and he said motion was jerky and than smoke was coming from belt area. did not look at it yet. odd. even 10 yr old original belt never made a squeak. if light hand pressure is applied, mower just slows down and even could stop. so belt does slip a lot. is it possible that new belt has more grip and just does not like to slip? standard v-belt. 1/2" width or maybe 5/8. old belt had many cracks but did not look real bad.