I'm fairly certain I saw a post on the forum about regrinding the needle on a carb mixture screw.
It involved boring a hole at a specific angle in a block of wood and turning the needle with a drill or press while a file was held on the needle as it just protruded from the block.
Can anyone help me find that post (or maybe I've finally lost it and it doesn't exist - hope not ;o) )
It's a repair described in the MTFCA carb book, I think? Steve Jelf shows how to do it here: https://www.youtube.com/watch?v=uTiStUTU9IE