Hello Doug
Old gasoline carburetor man Steve here.
The best float bowl fed carburetor information is in a Weber (Italian) carburetor manual. Hayes publishes a good one. This will not cover metering rods which are just variable orifice controlled jet openings. Rochester, some Solex, SU and Carter and Motorcraft manuals will have this info.
Basics are: Float level is Critical and will enrichen everything too the point of flooding or enlean everything to the point of stalling and backfiring.
Check/adjust this first.
Air bleeds are to introduce a metered amount of air into a fuel jet flooded mixing well to create an emulsified mix of air and fuel. Straight liquid fuel doesn't want to change speed and flow as quickly as air flow through changes take place - the lighter weight emulsified mix will have a quicker flow response speed.
A clogged air bleed will cause an enleaned condition - stall/backfire. Enlarged (BAD!) or missing air bleed can cause first a lean flat response followed by an overly rich condition.
On small governed speed engines there will be a richness idle needle adjustment AND a volume speed adjustment at the throttle plate or at a throttle plate air bypass passage screw.
Above the edge of the closed throttle plate will be a separately air/fuel supplied transition slot or series of holes. This allows additional fuel for the transition between idle circuit supplied fuel to main circuit supplied fuel.
This is subject to plugging and is very float level sensitive.
The main fuel circuit through the center fed venturi booster is usually not adjustable (except with air bleed and fuel jet change outs) and due to the larger openings gives the least problems.
Small governed speed air cooled engines I have seen almost never have an accelerator pump circuit, power enrichment circuit, altitude or economy enleanment capabilities.
Problems in order of occurrence are: air leakage at mounting, too low of float due level due to fuel absorption or pin holing of the metal, dirt/gum clogging of the air bleeds, gum/metal corrosion clogging of the fuel metering jets or into the throttle bore openings.
With no manual: carb spray all passaged for being clear. Use the same spray to check for mounting air leakage if it is run-able - should be no speed changes. After inspecting the float SET IT OBVIOUSLY TOO HIGH and try it. Keep working the float level lower until you are satisfied with the overall performance.
The fuel jet/s will be visible toward the bottom of the a casting in the float bowl, or with screw in removable upper air bleeds underneath down in the bottom of a fuel mixing well.
Let me Know
SteveU.
PS: Most anything battery start capable will have a charging circuit. This is usually used to power an electric fuel fuel shut off solenoid in the main/idle fuel well. It is the berries when you run into an solenoid with a sticky pindle, bad grounding circuit, intermittently open coil - all of these will drive you to drinking!