i do think its a fuel issue maybe a fuel line or connectors?
- yes -
start from the tank and double check the clamps and fittings.
the squeeze bulb is often the culprit if it is old, hard and brittle.
Remove the hose end fitting at the motor and pump the gas
by hand into a clear plastic bottle ...... This will give you an idea of any restrictions.
if WATER and other crap goes into the bottle, time to clean the gas tank.
remove the carb bowl to check for water or gunk.
This is when a good quality clear inline fuel filter is beneficial.
check the O-rings in the quick disconnects.... if they are chipped, cut, cracked or bad,
air can be sucked in at this connection - resulting in less than favorable fuel delivery.
also, do you have the little vent screw on the gas cap ??? this must be
loose/open when running the motor.
when was the last time you had the fuel pump apart ??
it may have some issues: hard/brittle/cracked diaphragm, clogged filter screen,
sucking air through the gaskets, etc.
if you have the standard issue gray fuel line, there are reported problems
of the inside liner coming "unlaminated" causing a portion of the
plastic liner to interfere with the fuel flow. To check this, remove the clamps
and fittings - cut the hose back a couple of inches, reassemble with new hose clamps.
a couple of good videos on the old YouTube: (there are many).
https://youtu.be/8GJxpXfakP4
https://www.youtube.com/watch?v=PglRQK0at1o
check all that when you can - report back with your findings.
if I missed anything, there are many very talented and experienced motorheads here to help you.