Re: need help identifying part, where to purchase
That carburetor rebuild kit won't do you any good. The parts aren't for the NT carb.
The missing screw is not a needle type like mixture screws. It is blunt on the end and acts as a mechanical stop to adjust engine idle speed. I don't know of any suppliers that sell just that part. They can be made but you'd need one to copy. The length is critical as is the diameter of the end that goes in the throttle slide bore.
I'd order a new carb and have spare parts. You'll want to order and NT carburetor for an exact replacement. Some other aftermarket carbs will require a different throttle cable.
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