just went through a 540c I purchased at auction, 450 sep. hours, 900 engine. there was a few things that needed attention like the ujoint on the bubbleup auger,one cross was done. check by turning auger back and forth, with new joint there is no play. not fun to change! turned the chopper blades to sharp side and replaced the finned ones.did a concave check and half an inch on the screen equated to 1.5 inches between the rotor and concaves.make sure you run the concave to zero, mine would not go that close because it was binding on the right side. owner before never checked I guess.must have been hard to thrash any kind of wheat.tension springs on the feeder chain were both broken.couple of the belt idlers were close but not perfect,easy to align.the engine oil dip stick is tricky,lift out so you break the oring seal on the top,then check the oil. concave selection is a grey area ,and make sure it has the precleaner extension . looking forward to putting this unit in the field.