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for fuel to be sucked in the crankcase from the carb it must have sufficient vacum during the uptroke of the pistons . if anything is causiing a vacum leak other than via the carb
fuel pull in will be limited.
Test it by putting your hand on the carb face while a friend pulls the starter rope. you should feel the vacum.
have you pulled the dime size plug on top off the carb to clean out the 3 small drip holes of the LS circuit. ??? the side channel leading to the top of the carb is very narrow.
see diagrams of a different carb.. and your’s . Small carb’s side channel works the same way.
make certain the side channel is 100% and carb cleaner makes it to the top chamber. . with the LS needle out carb cleaner should exit the needle passage also when injected in the side channel
if you plug the needle threaded openning with a finger carb cleaner should exit freely in the drip chamber.
replace and seal the top plug rim with finger nail polish (any color works 🙂 )
make certain you have the proper carb gasket and the side channel is not obstructed stopping fuel flow up to the drip chamber.
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