The impact post driver we borrowed to build the fence is super simple. It's a one cylinder 35cc 4-stroke engine, Honda's basic powerhead. This time the driveshaft runs into a centrifugal clutch that powers a second piston to drive a post into the ground hit by hit.
It worked great, but we had one major user error problem with it.
With the post driver attachment, it's near impossible to stand upright. This is a problem because the oil fill gauge requires it to be upright. And as we found out, the thing in the oil fill hole that looks exactly like an oil fill line is not the oil fill line. This is explained to you in the user manual, but in a part not at all related to oil.
We overfilled it by about 3x, thus fully flooding the cylinder with oil. We pulled it apart, pulled the spark plug, drained the oil, put it all back together, and tried to start it 3 times. That should have worked, but because it was still overfilled with oil it would just flood again.
Long story short, we took it to get professionally cleaned, figured out the oil fill problem, and finished out the fence.