I have a craftsman model number 917.27690 26 hp 54" cut. The mower moves slow, I changed the motion belt but it seems very loose and it slips causing it to move slow. What should cause the belts to be loose even though I put new belts. Could it be the idler pulleys are worn causing it to be loose when I disengage the brake?

Hi,
Usually the bearing in the center of the idler goes although it could seize on plastic idlers and have the belt melt the idler. Diagram is below.
Peace,
Clarke