That black plastic square cap is hiding it. Never seen one like that before.
Distant some times you just need a new carb. Did you have one w/the air mixture screw covered by that black square plastic?. If you need a new 142f BGF on ebay is selling them for $108 plus ship...……...any time a 142/4f runs crappy 1st thing to do is to clean that idle jet out located below the idle screw adjuster. Most times that fixes it.