Farmall Cub

Hi, Awhile back I posted about my 154 running bad after it got hot.Well after 8 new valves and guides,and 180.00 later I got back and put it together.Went out today to cut grass and after about 3 hours it started acting like it was running out of gas.I have to check the carb tomorrow but I did notice that there was about 1/8 " of air bubbles in the sediment bowl.Is this normal?Thanks for any help.
Randy

check the vent in your uel cap. also a bad coil or condenser can also cause the same symtoms, in addition to dirt in fuel system.