Fox;
In the early days of tractors, there were three basic configurations used for two cylinder engines. One had opposed cylinders with opposed cranks. this one had an even beat & was easy to balance.
One had the cylinders in line but with both throws of the crank in the same direction. This one also had an even beat but was a Pill to balance.
The JD, as well as some others, had the cylinders in line but with opposed crank throws. Thes were also relatively easy to balance but ran with that uneven beat. They had two power strokes on one crank revolution, then the flywheel had to carry it for the next revolution. These were all 4-cycle engines.
The old Harley motorcycles had a two-cylinder V engine so it ran with a slightly out of time beat, but not as extreme as the JD. In the late 2-cylinder era, JD had a small utility model (435) which used a 2-cylinder, 2-cycle engine which sounded like a 4-cyl running.
