Is that a internal & external tank model ? other things to check :
1-Clean well carb, fuel lines, check fuel connectors for o'ring wear if using ext tank, might be sucking air.
2-If using internal tank, clean well tank interior, fuel line to carb, small mesh filter located inside of fuel cock, look for debris, obstructions.
3-Check fuel pump condition for cracked, dried, balloned, hardened diaphragms. Change
4-Spark plug for correct gapping, fouled, try with new if possible. Make compression test.
5-Worn, out of torque specs, dried out and hardened head gasktet, replace, clean all inside water passages.
6-Use fresh fuel and correct 50:1 fuel/oil ratio.
7-Could have an electrical related issue, when component heats up while on load, shuts engine down ?