Won't start
Loctite № 542 or 592. See
here and
here.
If you need a new air cleaner thermo sensor because yours doesn't work, send me a PM; I have some new ones.
Rough running when cold: choke problems. Show us another photo, this time of the choke thermostat and pushrod (with air cleaner removed). Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted
here for free download, and there's a choke adjustment article
here; you may well wind up needing replacement parts such as a new choke pull-off and/or put in one of the
Electric choke kits.