Reasons: clogged fuel pick up, clogged fuel filter, clogged fuel line, rubber hoses (if any) swelled up due new type gas, bad fuel pump.
Test: with a helper, disconnected fuel line at carb. Remove start wire to ignition. With bucket, have helper turn engine over and see how much fuel you get over several seconds. Measure pumped fuel and check manual to see if you have pumped enough. If not, start trouble shooting your fuel delivery system.
