we have run a gas 4400 now for almost 20 years look at the power shaft at the top of the variable speed belts, check for smooth run-no wobble may as well check the ground drive belts too look at all the rubber bushings on the screens especially the drive unit for the cleaning screens check the framing uprights where they rise above the front wheels-these like to walk away from the machine check to see if there has been bearing problems that have worn holes in the fan casing(one of our shafts rubbed a hole in there-we fixed with duct tape) the engine is a classic -the GM straight six, hard to imagine much trouble there ours has had ongoing trouble with the starter though a fun machine, i always look forward to harvest and this year we ran trouble free for our 200 acres of grain and soybeans..... good luck and feel free to ask away if you are checking out a machine -Mark in Canada.
