Sounds like you got problems with the control valve sticking. Most liking sticking is, crud in oil or frozen ice in oil. Many time in chamging oil, it hard to flush out all residue stirred up and it latter becomes lodged in valve causing erratic action. When you move the control rod, forward and backward, you are helping the spring overcome the sticking. In winter any moisture condensation or water, freezes and forms a stickie mess, like "sluch" to recondition oil, you need to thaw out the slush, so the moisture and oil separate (Oil floats on water). Loosen the drains in a warm shed and let the water drip until oil appears. If its crud, you may have to filter the oil, or replace oil again. A new control valve may also be needed.
I would do any or all the above before I tore the top cover off, for replacement of cam pin.
Charles Krammin SW MI