For your knife to be stalling the knife clutch may be slipping.

The knife clutch adjustment is the same on all platforms and should be set to slip only if knife jams.

Draw a line from the adjuster nut across the springs, friction plate and pulley side. Run platform in normal conditions and observe if clutch is slipping

To Adjust

1. Loosen the three pressure bolts on the lock ring.
2. Turn nut clockwise to apply more pressure to the clutch.
3. Retighten the pressure bolts to within 1 mm of seating

If applying more pressure to the clutch does not stop slip, the friction plates may be worn and need replacing.