"What is the correct RPM" every tractor I've used, that had a PTO, the tachometer will have 1, or 2 marks for pto. My Kioti has 2 marks; 540E (roughly 1800 rpm if memory serves), 540 (roughly 2100 if memory serves), and it will go up another 200-300 rpm. Now, 540E, isn't actually 540; its more like 480.rpm i think at the PTO but its what they consider "close enough, but most fuel efficent). If Kubota doesnt have two marked pto speeds; then it will have either a range or 1 speed on the tach, and from what I see on Google, its 2000-2200 engine rpm for the pti to be at 540. That is the "correct" pto speed. It doesnt mean you might not be able to run a bit below, and it also doesnt mean you can't press the throttle to the limit, and pedal down