This was posted on another forum, it might help you...

Has an interesting problem with my walbro carb on a ZDZ50NG, so I thought that I would post for your interest.

"Took a flight, everything was normal, but when I landed and went to taxi back to the flight line, the engine stalled. This never happended before. Although I thought nothing of it. Later, when I went to start up the engine flooded.
Pulled the plug three times and the plug was full of fuel. I gave up and packed it in for the day. Took the cowling off to find fuel coming out of the air inlet of the carb. Disassembly of the card proved to be a stuck metering valve. It was stuck open. Removed the assembly, cleaned and changed the valve and diaphram while I was at it. Works fine now."

Uduman