1980 Ski-Doo Shop Manual, Page 228Get this manual
SECTION 05 SUB-SECTION 02 (DRIVE BELT)
10Belt" Flip-Over" at high speedCAUSE a) Pulley misalignmentb) Belt excessive speedREMEDY a) Align pulleysb) Using unspecified type of beltReplace belt with correct Bombardier belt(