Art and Roger,
The horizontal engined tractors have a nominal air gap of around 0.018 inches, while the vertical motors usually have a larger nominal gap of 0.020 to 0.024 inches.
Also, Deere recommends engaging and disengaging the PTO at part throttle, but using WOT while mowing:
From the description of the drag on the engine when engaging the PTO when cold, you may have the gap set too small and the integral brake in the PTO is dragging until everything expands with increased temperature...
Chuck
The horizontal engined tractors have a nominal air gap of around 0.018 inches, while the vertical motors usually have a larger nominal gap of 0.020 to 0.024 inches.
Also, Deere recommends engaging and disengaging the PTO at part throttle, but using WOT while mowing:

From the description of the drag on the engine when engaging the PTO when cold, you may have the gap set too small and the integral brake in the PTO is dragging until everything expands with increased temperature...
Chuck