After rebuilding it isn't all that unusual to get dirt introduced back into the carburetor upon 1st startup. Be sure to plug and keep the inlet fuel line clean while the carburetor is off of the vehicle.
Check for excessive throttle free play by spraying carburetor cleaner at the throttle shaft. If the RPM changes, or the idle smooths out, then you have too much wear and you will need to add bushings to the throttle body.
When buying used carburetors look for any sign of white corrosion on the outside of the carburetor. This is a sign that the carburetor sat in the weather. The inside is probably much worse and probably cannot be used.
Check for proper main jet size by inspecting your spark plugs. Gray is good, black is too rich, white is too lean. Change the jet one size, drive 20 minutes at sustained speed, then check the plugs again.
Inspect your idle mixture screw for any damage to the tapered end. Replace when the tip is not completely smooth. Fortunately the idle mixture screw is still available.
Do not over tighten your idle mixture screw. Doing so will damage the screw.
Ethanol will leave residue behind in any of the orifices and passage ways. Use small wire to clean out the passage ways, but be carefull not to enlarge any orifice.
Gasoline will turn to varnish over time. Cleaning your carburetor and not the fuel tank under this condition will result in the carburetor needing rebilding again.
It now takes more gasoline to run the same mile. Cheat to the high side when setting things like the float and the main metering jet.
The spark control valve is designed to work with certain distributor systems. Mixing the two systems may not work out so well.
Never bead blast your carburetor parts. The media will get caught in the passage ways. Soda blasting is ok, but be sure to blow out the passage ways and wash clean after.
Diagphragm covers are usually warped. Grind flat and/or use the repair plates that are included in our 1100 hardware kit.
Test your float by immersing in hot water and look for bubbles. The hot water will cause the inside of the float to expand and air will be forced out of any hole.
Use a straight edge to check the float bowl for warpage. To correct sandwhich the float bowl with two pieces of flat metal stock on the fange side and one on the top of the float bowl and place in your vice. Tighten the vise to put a small amount of pressure on the float bowl. Use a torch (propane, or otherwise) and heat up the float bowl. Be careful not to get it so hot that you ruin your carburetor. Let cool.