The above video is of a home built tractor powered by an old hit and miss engine. Hit and miss engines were one of the earliest internal combustion engines, and in their day they were widely used.
As you can tell from the irregular popping the combustion, or power stroke, did not happen on a regular interval. That's because a hit and miss engine is a type of flywheel engine and combustion would only occur when needed to keep the flywheel turning at an average speed. Wikipedia has a fairly good description as to how they worked.
If you're interested, Liney Machine has a number of interesting model engine kits, including several hit and miss engine models which range from $225 to $475 in price. Below is a video showing their Coles hit and miss engine model in operation.