The bolt definately does not belong.

Some carbs have the adjustable main metering jet; others simply have a hex plug which covers the access hole for the main metering jet. Without knowing the tag number, no way to know; and even with the tag number would have to pull a print off of a 500' roll of microfilm.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop