Not known to be good runners, and not real supportive of John Deere traditional quality. Jumped their 40 and 420 line of 2-cyl upright engines with good standing, over to the new line of more cylinders. Took awhile to make that transfer for a good engine in the small tractors.
Most of the tractor is a 4 cyl engine in the 420/430 tractor. The basic tractor thus is tried and true.
The diesel engine, if you do a google search here, didn't fare too well. Maybe the gas engine was better.
And check out the "similar threads" at the bottom of the page here.