Thunderbird 900 stalling when put into gear

I recently disassembled my thunderbird to do some work, paint etc. Now during reassembly I have a few issues. (Will make a different thread for each issue).

In neutral: engine starts fine. But when but into gear it immediately stalls. It jolts a little and dies.

I thought it was the side stand so I tested by keeping it up and starting in first gear. It tries to start but nothin fires up.
Is it the side stand then? What can I do to fix the issue? Do I need to order a new side stand switch...

Thunderbird 900 stalling when put into gear