When the engine is running, look at the float glass, make sure the level is right. If it's not within 1 mm of the center line of the glass, you'll need to take the carb apart to adjust the float level. A repair manual will be useful here.
Checking
If the float level is OK
If the fuel level is within 1mm of the dot, it is already at the correct adjustment.
Adjustment
IMPORTANT: High fuel pump pressure can cause a high float, so if it is high, perform the Fuel pump pressure test first -- before taking the carb apart to adjust the Float Level.
1. Remove the top of the carburetor. See Carburetor Top Removal for instructions.
2. Turn the top upside down (and level)
3. Measure that the float hangs with .418 inch space per this diagram
4. if necessary to adjust float, bend the tang under the float pivot pin.
Reassembly: Put the top back on in reverse order of dis-assembly. Just tighten the bolts enough to compress the lock washers. No more.
Then perform Idle Speed and Mixture Adjustment - which will change due to changed float level.
Bad Float
See main article: Float repair