Is the routing diagram on my tractor (and in my owner's manual) wrong?
I am following the diagram from the front of the tractor (engine pulley) to the rear.
The "top" pulley is the one on the tranny with the fan on it.
hold the shaft while trying to turn the pulley to check the spline on top of the box has not stripped.
They are designed to do this to protect the box.
As previously mentioned double check the belt is properly seated in the box pulley and also on the engine pulley.
Run your fingers around the pulley to make sure the belt is properly seated in the pulley as it can pop off and sit on top of the pulley however when that happens the belt usually runs quite slow.
The pulleys do look wrong, idlers come as flat & V profiles, the back of the belt runs on flat idlers & the V runs in V idlers which is not happening in the video.
Numbering them 1,2,3 from the new pulley as No 1
The belt would normally go V side around No 1 pulley then flat side around No 2 pulley then around the engine pulley then back down to the No 3 pulley but running on the other side of the pulley.
The belt keepers are free to move around the pulley once the nut is loosened.
Routed that way the existing belt would pull tighter.
Have a close look under the mower for wear marks in the paint.
If there is a polished section where the belt has been running and now the belt clears that place then the routing s wron.
I find it a lot easier to put some glad wrap over the fuel filler then screw the cap back on to stop fuel draining out of the tank vent, remove the battery then stand the mower vertical so I can work in a comfortable position and see clearly what I am doing without eating dried grass