Because mot mower companies make a big loss on small parts, brakes are considered to be part of the transmission & not the mower
Very rare for the brake to fail completely
Usual problem is the bake locking on
using the diagram that Star posted above
1) check that the arm 41A moves when your foot in on the brake , if not trace back the rod which fits in the hole and adjust it ( there will be a spring & adjusting nut )
The brake should release just after the clutch takes up the slack in the drive belt ( You can't brake & accelerate at the same time )
2) If 41 A moves to the limit of it's travel but the brake still does not work then adjust nut # 43 tighter.
3) If the are 41A moves as far as it can and adjusting the middle bolt makes no difference then remove the entire caliper ( bolts 42 & 42a ) and check that pins 39 are free to move
Check that the disc can slide on the spline.
NB
The brake locks the diff so the wheels can only turn in opposite directions.
It does not stop either wheel turning
