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Old Iron: 1957 John Deere 720 standard diesel

Lance Phillips for Progressive Forage Published on 12 July 2017
1957 John Deere 720 standard diesel with V-4  pony engine

The history of John Deere is one that has been told many times, and it is one of the earliest farm equipment manufacturers still in business today.

There are many reasons for that but, in my opinion, the two main reasons are customer loyalty to a great product and the people at the top making the tough decisions to continue the great legacy of the John Deere brand.

We have one of the classics, a 1957 John Deere 720 standard diesel with V-4 cranking engine or pony motor. There were only about 4,500 standard models produced and, of those, about 3,500 were diesels.

The 720 model was available in row-crop (some with wide front ends), high-crop models and standard versions, having an adjustable front end or a fixed front end. These 55- to 60-horsepower machines were powered by engine variations of gas, LP gas, diesel and a very rare all-fuel version that would run on other petroleum sources.

With just over a 6-inch bore and stroke, these big diesels let you know you’re really doing something when it’s under a load. These tractors were manufactured with pony motors as well as some with electric starters.

Both have their advantages, but we tend to lean toward the pony motors because we enjoy a challenge at times and they are quite the topic of conversation for folks who have never seen or heard of such a thing.

It is certainly hard to mistake the unique and distinct sound of a two-cylinder John Deere. These engines are somewhat peculiar as they run horizontally instead of vertically like most engines we are accustomed to seeing. Farmers had plenty enough horsepower to get their work done and do it from a very comfortable operator station as well.

I’d say the float ride seat made long days in the field a bit more enjoyable. These tractors were equipped with a hand clutch, individual foot brakes, cigarette lighter, live power take-off, power steering, and some had three-point hitches, as ours does.

A friend of ours had told us of an old John Deere tractor sitting in a field near Natural Bridge, Virginia, in the summer of 2004. I wish you could have seen where this tractor was when we found it. It was out in the middle of a pasture with trees that had fallen down all around it.

Surprisingly, the sheet metal was in perfectly straight condition with only some surface rust. It was obvious the tractor had seen a rough life, though. We couldn’t really get a good idea for how long the tractor had been sitting, but we soon discovered the diesel engine was stuck.

There were also massive wheel weights on the inside and outside of each rear wheel, so it had definitely done some work in its time. We went back in a couple of weeks with a rollback, a long cable and several chains to get it loaded and start all the work ahead of us.

Some good tractor buddies of ours who are very familiar with John Deeres (and still do a lot of farming with two-cylinder models) told us to bring the 720 over to their shop and they would help us work on it. After some initial disassembly and diagnosis, it became apparent the diesel engine would need to be completely rebuilt.

When we had all the major repair work complete, it was time for paint. A good friend of ours took care of the chassis, etc., and we had our local Ford dealership paint all the sheet metal.

We thought the cranking engine or pony motor was going to be in good working order – but later on we found out different. One day, we went into the shop to find a puddle of green water under the tractor.

One of the head gaskets on the pony motor had failed, allowing engine coolant to run all over the pulley/clutch side of the tractor, leaving stains on our new paint job. We were able to track down a good running motor and replaced the one with the bad head gasket.

There is a section of the hood that swings open to reveal a very small gas tank for the pony motor, which sits just in front of the dash and atop the diesel engine block. When you crank the pony motor, it starts at an idle; then you slide a small lever to allow it to open to full throttle in excess of 5,000 rpm.

You then pull back on the compression release lever for the diesel engine and slowly pull the lever right beside it to engage the starting drive clutch, which engages the huge flywheel to turn the diesel engine. After the diesel engine has turned over a few times, throw the compression release lever off, and pop, pop, pop, you’re running on diesel. You then have to manually turn the ignition switch for the pony motor off and you’re good to go to work.

This is truly a great machine, and I hope each of you have the opportunity to check one out sometime.  end mark

PHOTO: This 1957 John Deere 720 standard diesel with V-4 pony engine is prepared to head out to the 10th annual show of the Old Glade Antique Tractor Association in Abingdon, Virginia. Photo by Lance Phillips.