When I work on the fuel system and fixing to take something loose I always have a large bolt to insert it into a rubber fuel hose somewhere near the tank. I pull the line and quickly insert the bolt to keep the fuel from running out. It won't come gushing out as much as you think. When finish pull the bolt and hook it back up.
Are your idle mixture screws adjusted properly on the carb? You might need to richen the idle circuit in order for the motor to stay running.
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