Obviously, you’re not a rookie, so you have the tank gas cap screwed down snug. My first guess is the rubber check valves behind the intake manifold, that allow tank pressure to build. I have seen some that deteriorate and don’t seal right. If you don’t build tank pressure, no gas gets sent back to the carb and the engine dies. The tank primer just sends enough fuel to fill up the carb again. It doesn’t pressurize the whole tank.

nothing scary…        just pull the carb    pull the back plate and behind (trying not to break the gaskets)     are the flapper valves feeding the pressure pulses to the side nipple. see parts diagram

keep it simple first… check for air leaks with soapy water

btw  did you  clean the low speed cct and      clean   the  high speed nozzle    looks like the engine is starving

the ls side channel on those carbs  has a tiny channle  to the top…. blow with carb cleaner & air    and  check under the  top dime size plug  to see if the the  small idle drip holes are clear.

if your model has a fuel  filter remove it for a test run..

to suck fuel out of the carb air must  also enter the carb to replace emulsified  air/fuel sucked out… make certain any carb hole to balance  carb air supply is not blocked.

Pretty certain I have a set  in my  old parts so if you find yours is  defective send me  PM.. I can probably send one in a regular mail envelope…free 🙂  after I find it

without paying parcel postage   $$$$$  🙂

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