Dave -
here's the inside of the box, note on the left side fork one corner is slightly worn, if yours are worse then that they need building up as Wrenchbender sez .... also note the jamming is always a result of sloppy shifting, once you see the inside you might get a better understanding of the way to handle shifting so it doesn't jam .... also make sure the spring is in position and not broken and that in neutral the forks are perfectly lined up
Bill
