If it is a Hitchcock kit, the first thing I would do is to send Hitchcock an E-Mail that explains exactly what is happening with the shift lever. That is, something like,
I have a Royal Enfield 65......
The shift lever does not shift the gears when it is moved.
The lever seems to be spring loaded and it returns upward rotating at least 60 degrees from a horizontal position. It seems like it is not connected to anything except for the spring.
Can you give me an idea of what could be wrong and what I would need to do to fix it?
Also, attach the short video you posted earlier.
(This one)
https://www.youtube.com/watch?v=tZ7sNugqa9Y&feature=youtu.beIf anyone knows how to fix it, it would be Hitchcock and from what I've heard, they are very good about answering E-Mails and answering questions.
IMO, that lever should have some sort of positive engagement with the shift plate which has the milled irregular shaped slot cut into it.
There should be a cam follower that goes thru that shift plate's slot and the cam follower should move the yokes that move the gears from side to side.
As the gears move from side to side, dogs on the sides of the gears engage or disengage from the dogs on the side of the adjacent gear. That's how the gears transmit power thru the gearbox.
(Maybe you already know all of this but I thought it was worth mentioning.
Now that it is, it looks to me like the shift lever is not engaged with the shift plate. If it was, it could not move to a position that is over 60 degrees upward when the lever is released.)