Atlas 750 gearbox mainshaft play / end float

Hi all,

I have a 1964 750 Atlas that I want to get back running.
I was going to remount the primary chain when I noticed that there was play in the clutch assembly. I disassembled the clutch and found that it was the gearbox mainshaft moving lengthwise.
Couldn't find anywhere stating if there should be play here and my intuition says that there shouldn't be any play at all.
Here's a link of a short video I made of the play:
Before I start taking the bike further apart I just want to check with you if I am correct with it being a problem and also what what could be causing so much play.

Thank you in advance!

Br.

Martin

Assuming the AMC gearbox, the mainshaft is locked into place by the timing side bearing and nut. It should not move at all. Most likely, your nut is loose. Remove the outer cover to check.

If it's a laydown GB, I have no idea.

If the issue is as stated by @marshg246, (which seems likely) the following tool makes tightening the lock ring nut much easier.

https://andover-norton.co.uk/en/shop-details-2/18608/gearbox-lockring-assy-tool-01-5800-

Clutch cable need to aligned with the clutch operating lever for smooth clutch operation.

It is an AMC gearbox. Sounds plausible I'll try to have a look inside the gearbox and see if the nut is loose.