Tecumseh pony motors
Back in 1990, I was farming using a 530 Case and an “AR” John Deere. In an effort to improve time and fuel efficiency, I purchased two 70 John Deere diesels. Serial number 7032670 was a row crop and 7018465 was a wide front. Both were in rough shape.
I started working on the row crop first. My neighbor, Lester Nodecker, and I cleaned it up the best we could. After taking the cover off the injector compartment, it didn’t take long to discover that the block on the main engine was cracked and that someone had made a poor attempt to weld it. I ordered a rebored block from Central Tractor and sent the injectors and pumps out to be rebuilt. Meanwhile, the pony motor wouldn’t run, so Lester and I took it apart to rebuild it. that was when we found the starter motor was cracked, too. At this point, the parts came in for the main engine, so we put that together.
To start it the first summer, I used a flat belt hooked to my “AR.” This was inconvenient, to say the least. This was to be a working tractor and I didn’t plan on spending the money it would take to buy a used pony motor. My luck hadn’t been very good in buying used parts, so I came up with another idea. Why not adapt a different motor to the starter transmission? I have worked as a machinist for 30 years so that I could afford to farm. I also had a machine shop at home. I started looking around for a 10 horse single cylinder engine on a snow blower. All I could find were 8 horsepower engines. I measured the 8 horsepower engine and figured it would fit in the space where the pony had been. I also checked the rotation of the Deere pony motor to be sure it turned the same direction as the new small engines, but I still wasn’t convinced that 8 horsepower would be enough. I was sure I could mount a 10 horsepower engine in the space I had, but the same question applied—would a 10 horsepower engine be enough to start the 70 diesel? All my friends said, “It will never work.” That settled it and I ordered a Tecumsehf model HM1000 with electric start. In order to be able to continued using the 70 row crop, I started working on mounting the engine in the 70 standard. After building a bracket to support the starter transmission, I started working on mounting the Tecumseh engine in the tractor.
I bored out the original flywheel to fit on the starter motor and then assembled the original clutch and the flywheel to the new starter motor. The next step was to mount the starter assembly in the tractor. I had to build a new exhaust manifold with a sharper 90 degree angle and the throttle linkage had to be moved about 1/2 inch to clear the dash. Next, I shortened the crankshaft on the starter motor about an inch so I could move the engine in as close to the starter transmission as possible. After fitting the hood in place, I tried to mount the pony door. It was close, but it wouldn’t fit. This meant I would have to fabricate a door and find a way to mount a gas tank that I could fill. The gas tank came first as I needed it to see if this brainstorm of mine would work. After some measuring, I found I could mount the tank that came with the engine on a slide so it would be under the hood but would slide out to fill.
I adjusted the starter clutch, hooked the exhaust up to the intake preheater, did the electric wiring and then it was time to see if the new starter could crank a 70 diesel. Everything worked better than I expected. The 10 horsepower engine cranked the diesel easily. In fact, I could start the starter engine with the transmission engaged. The next test was to try to start the 70 standard. It was in bad shape and this would be a real test.
Before I could get the tractor started, I had to rework the starter motor governor so the starter would run faster than 3,600 RPM. After that, one more try and I got the old 70 running. To finish the job, I built a flat pony door with a cutout for the new engine. As you can see in the picture, it looks a little like the original.
After patting myself on the back for a while, I moved the whole starter setup to the 70 row crop I had rebuilt. It started this tractor with ease. My total cost of this conversion was $400. Because replacement is affordable, I have used the pony motor to move the tractor in tight spots in the shed. I have also used the pony to drive the tractor home after I broke a diesel fuel line in the field.
Due to moving and a number of health problems, it took until 2000 to get the 70 standard fixed. When I did, it got the same starter setup, a 10 horsepower Tecumseh engine. The paint job wasn’t meant to be as good as new. They were meant to be working machines, painted to look good from the road and to prevent rust. There are those who won’t like these tractors, but they draw a lot of interest at the local show.