D6 9U electric to pony starter?

Probably broke the bendix. Those old inertial type drives aren't the strongest design, though I have never had trouble with ours here and we always start them with 12 volts by jumper cables. That should be hard on them but never broke one yet.

Your biggest challenge is going to be getting the starter pulled back out of the housing after taking out the retaining bolt on top with the jamb nut. Have heard these can be tough to get loose. If it absolutely won't come out, it looks like you might be able to pull the field housing off the starter with the nose housing still in place and then remove a separator plate to allow you to pull the armature and drive assembly out of the nose housing. Shouldn't be out much if you have to go that route.

Sorry, I cannot scan the relevant parts book pictures. If you have a parts book, the pony starter is in the attachments section at the back.

Would help if you supplied s/n.

Usually it's the spring that goes, especially if you have been using 12v for starting.

I'd post the push button version but the attachment function is screwed up again to where it will only accept one.