Starting to disassemble a rough WD-4S. Before I damage something, how does the choke or choke knob come out / off so you can remove the engine cover?

We are speaking of the acorn shaped plastic knobs...correct?
If so you are lucky as they are often missing.
They are threaded on regular thread...turn off counter clockwise.
You may have to reach behind the knob with bent tip needle nose pliers
to prevent shaft from turning. Bag,Tag and keep in a safe place
until needed for reassembly.
Louis

Thanks, makes sense. Wanted to make sure before I scratched the shaft up. Lot of fasteners are rusted. The motor laid around in a barn for years.