Troublesome Tillage with a 1955 John Deere 70 Diesel Pony Start and a Graham Hoeme Chisel Plow

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Golden oldies, ready for work. Rodney Ahlgrim’s 1955 John Deere 70 diesel pony start and 10-foot Graham-Hoeme chisel plow.
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Rodney and his daughter out for a spin on the 70 in 2010.
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The John Deere 70’s Wico magneto, before the rebuild.
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The John Deere 70 at rest.
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The 70’s Wico magneto, after rebuild.

If you love working with vintage equipment, patience, mechanical aptitude and a good sense of humor are great things to have. I feel very fortunate to be able to exercise our vintage farm equipment, some of which has been in the family for more than 50 years, on several acres that were homesteaded to my family in 1883. As can be expected due to its age, the equipment can command a lot of attention — especially when a few decades have passed since it was last used.

Not long ago, it came time to break out idle equipment. Our high-clearance 10-foot Graham-Hoeme chisel plow hadn’t seen the field for more than 20 years. One tire still held air but the other was completely rotted; both needed to be replaced. I was able to dig up truck tires for the 17-inch wheels but 1950-something rims don’t facilitate installation of tubeless valve stems, an idea that might have been in the most top-secret “computers” of the time.

I enjoy the opportunity to “time travel” through my surroundings. Rather than pay someone to mount and dismount the tires, I got my manual tire tools and proceeded to change tires the “old school” way. At this point I refer the reader back to the part of the story where the implement sat for 20 years, including time spent at the edge of a slough, where the tire bead rusted to the rim. Tearing that bead loose required the ambition of Moses crossing the desert to find the Promised Land.

After unsuccessful attempts to work the bar under the lip, assistance was dispatched in the form of a sledgehammer driving away at the concrete-like bond until, with a kind of duct tape-tearing sound, the seal was broken and the tire removed from the rim. Installation was good for my memory as I soon recollected how difficult 8-ply truck tires are to bargain with. With sweat pouring off my brow, I cleaned the lip, slimed the bead with a dishwashing detergent solution and installed the “new” tires on the rims, taking care not to pinch the new tube, then aired up the tires and checked for leaks.

Facing a few challenges

I then turned my attention to our 1955 John Deere 70 diesel with pony start. This proved challenging, as the carburetor on the gasoline pony engine was on its original assembly. Years of climate changes and traipsing through the dust of the Sand Hills had produced rust and sediment that altered fuel delivery from a finely tuned mist to what I am convinced was more of a controlled flood. Adding to the reality show challenge were exposed bare plug wires of the same vintage sprouting from a Wico magneto that has rarely seen a shed in 50 years. We’ll revisit those two points later in this article.

After fluid levels had been checked and the tractor verified field-ready, I went back around to the operator’s platform. While stepping up, I turned my head and noticed a certain amount of flatness on the bottom of one of the chisel tires: I had pinched a tube. I grumpily removed the tire, loaded it in the back of the Dodge pickup and drove to my brother’s, where I used his stationary tire changer to fix the tire. The appeal of “old school” took a short vacation.

Off to the field

The next morning I awoke ready for some long-awaited wheel time. After I installed the tire on the chisel, I made revolutions for the field. Upon hitting the dirt, I was pleased that after its lengthy sabbatical, the tractor huffed through the field at 3/4-throttle, sometimes puffing black smoke, with the implement cylinder nearly to the depth stop. An engine overhaul of 0.060 pistons and tweaking the fuel rail up a couple of notches — my college project in 1985 — really made a difference at the drawbar.

Though the framework for a cloth buggy top remained intact, the canopy had long since lost the battle to the elements. I scrounged around and found my old straw cowboy hat from one of the “urban cowboy” reprises of the 1980s. I took it outside, blew off the dust and reformed the brim like a straw hat. As the heat rose, it was nice to have the hat to keep the sun off of my face and neck. There was a pretty brisk wind that Saturday. About mid-afternoon a gust came in, levitated the hat from my head and put a side-spin on it. The hat skipped merrily across the clods and headed out of sight. After a quick personal assessment of my emotional attachment to the hat, I decided that in triple-digit temps, my butt was more attached to the tractor seat than my heart to that old hat.

Lost in time

I made pass after pass that afternoon, as the sun climbed high and the heat of the summer day rose. I enjoyed the time in my 1950s-era world, only checking into present day when vehicles traveled down the oil well lease roads. My pride swelled as people stared. Were they remembering fond memories, or just marveling at the idiot working out there with no cab or A/C?

With the combination of the higher horsepower, equipment age and heat, the tractor clutch eventually started slipping with a grinding howl and the engine temp rose to near red-line, necessitating a brief cool-down every several laps. During one of those pit stops, I noticed I was attempting to seed a new chisel as a shear bolt had broken and left one of the now irreplaceable shanks somewhere in the 20 acres I had just crossed.

It was a fine stroll across chunks, trying to recover the missing iron in an effort to avoid an apparitional visit from my late father, chewing me out for carelessly breaking his equipment. I thought I saw three of those shanks sticking up from the ground, but it was one of those “oasis in the desert” things, as all that I found were chunks formed into polished arcs by the tines. The shank was later recovered and reinstalled.

Oh, brother!

Tightening clutch discs is normally not a big deal as the cross-engine design on the 2-cylinder Deeres allows the clutch to be changed easily and adjusted without the peskiness of splitting the tractor. However, with the pony motor in the stubborn condition it was in, I might get a couple good starts in a day depending on temps. Otherwise, the equipment was little more than a really big paperweight. So the only time I shut down the engine was at lunch when I drove to the house, avoiding what would otherwise be a long trek through the overgrown pasture for a return trip to the tractor, where the pony would likely refuse to start.

Following lunch one day, I went back to work. After adjusting the clutch and a couple of crank-and-choke sequences, it was clear the pony wasn’t going to start. In terms of mechanical aptitude, it wasn’t one of my shining moments, especially in that I know this particular tractor so well. I started disassembly and diagnosis on the pony magneto, primarily looking for a 6-volt power feed (note: magnetos don’t use battery power). I proceeded to remove and test wires from the back of the tractor’s master electrical switch, while also using a battery charger to boost amps to get a little additional rotational motivation to the starter motor.

When I found no voltage, I proceeded to use jumper cables to bypass switch current to the mag. With all of the electrical wiring in disarray, when I hit the starter, the cranking engine fired and idled up. Panicked, I rushed around re-landing all the wiring, removing cables so I could start the diesel engine. The rest of the day went well and I finished off the field and returned to the house just before sundown. After showering and washing the dirt off, I had a really good farmer’s suntan with a nice red glow.

Keeping it real

The next morning while I washed the tractor, a gentleman pulled into the yard to ask if he could get some water. As we visited, he said he had been in one of the trucks going down the lease road the day before, scrapping a dismantled center pivot system on a neighbor’s property. As he looked over the vintage setup, he told me how he enjoyed watching and listening to the equipment work and said, “Don’t make the mistake I did.”

He told me that he had a 2-cylinder John Deere that had been his father’s and he had meticulously restored it to better-than-new condition in honor of his dad. He said sometimes he regretted it, as now the tractor was only driven for show, not for actual fieldwork. I saw emotion on his face and heard it in his voice: He missed working the old tractor. Had it not been for the squirrelyness of the power steering on John-John, I might have let him take a couple passes just to reconnect with his past.

After the tractor had been washed down and the chisel teeth sprayed with aluminum paint, I called this project done. When people asked how my weekend went, I told them the truth. “Heat was miserable, equipment was stubborn, had to fix things to keep going … Gosh, I had a great time!” FC

Raised on a family farm in central Kansas, Rodney Ahlgrim now lives in Kansas City, Mo., where he works as a sales engineer for electrical power systems. In his free time he enjoys writing humorous essays and periodic visits with his family to the home place. Email Rodney at

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