WA-1 Leaks Out the Throttle Shaft
This could be cause by a couple of things.
The carburetor could be percolating.
A test to know if it is indeed “percolation” (heat soak): touch the carburetor bowl when it begins to leak. If it is not too hot to touch comfortably, it is probably not heat soak.
The other possibility is that the carburetor is simply flooding over. When excess gas runs down the carburetor throat, it accumilates at the throttle valve and runs out the shaft.
Check for a bad float – Heat up a pan of water just prior to boiling and immerse the float. Any hole or crack will show up with bubbles.
Float level – Check the float level and float drop.
Move the float up and down by hand to make sure there isn’t something catching, or binding.
Bad needle & seat – Dirt may have gotten into the needle & seat, which happens often after a rebuild. Check the gasket under the seat to be sure it isn’t cracked. Make sure there isn’t something under the gasket. If the needle has a viton tip, then it may be damaged by the ethanol, or could have been damaged with installing due to too much pressure on the needle.
Fuel pressure to high (new pump would especially be suspect). Test the pressure and compare with the specification in your engine manual.
Idle Mixture Screw Doen’t Make Any Difference When Adjusted
How Do I Know When the Throttle Shaft is Worn
Once you take this plug out there will be a tube inside that will screw out.