When the starter motor drive and the foot pedal linkage do not return after the engine starts, there are four possibilities for trouble; three involve a spring used to return a mechanical device to rest; one involves something bent.
The foot pedal linkage has a visible spring (Number 1) just above the starter motor housing that returns the pedal and linkage to rest. The linkage is separate from and not mechanically connected to the starter motor stuff. When you mash down on the starter pedal, all the linkage does is push on the lever that moves the yoke inside the starter motor. That starter motor lever then presses the button on the electrical switch mounted on top of the starter motor housing.
The electrical switch mounted on top of the starter motor also has a spring (Number 2) that returns the switch button and electrical contact to rest.
Finally, there is a spring (Number 3) that is internal in the starter motor that returns the starter motor armature and bendix drive to rest.
You can test to find out where the problem may lie. Try it first with the key off so the engine won't start.
Test the foot pedal linkage by mashing down on the starter pedal until the last possible moment before the starter motor begins to turn the engine. Take your foot off the starter pedal and see if everything quickly returns to rest. It probably will, but this is the easiest test of springs and linkage. Try it several times, as mechanical gremlins have a way of avoiding detection. If the foot pedal and linkage do not return to rest quickly, the problem most likely lies with the foot-pedal linkage. Check for bent or binding things.
Next, with the key off, mash down on the starter pedal to engage the starter motor drive pinion into the flywheel and run the starter motor (not for very long, of course).
If the starter motor won't "hang up" with the key off, try later with the key on.
With the key off, if the starter motor "hangs up", check to see if the foot pedal linkage is binding or loose by pulling up on the foot pedal with your toe or hand. If the linkage is loose, but the starter motor is still "hung up" and running, is the starter motor still engaged with the flywheel and trying start the engine or is the starter motor just sitting out there spinning away wasting battery?
If the foot-pedal linkage is loose and the starter motor is spinning away, doing nothing, not turning the engine over, then the spring (Number 2) inside the electrical switch on top of the starter motor is bad. You said you already replaced the electrical switch, so I doubt that this is the culprit.
If the foot-pedal linkage is loose but the starter motor remains engaged and is trying to start the engine, then I would suspect the internal spring (Number 3) that returns the starter motor armature to rest.
If the foot-pedal linkage is not loose when the starter motor "hangs up" then either the foot-pedal linkage spring (Number 1) is bad, or the linkage has a bind somewhere. If you have lubricated the linkage bearing points, then the linkage is REALLY binding somewhere. Sounds like the hawnyocks that don't know s**t about stovebolts may be at fault.
Let us know.
