YFA Carburetor wont start

[mat in tn]

Had a similar issue after I messed with the fuel lines and tank on my truck with the YFA. I would start it with a gas can in the engine bay, or pouring fuel in the line from the top and hooked it up to the tank after it ran for a while, or if I had cranked it for 10 or so minutes. Not a carb guy by any means but to me that meant the fuel system was bad on the tank end.

let's keep this simple. drive the truck around a bit to get it up to operating temp. as close as you can to the temp where the problem occurs and then park it back at home and wait the same time as you would expect to have the problem. then open the hood and remove the air cleaner but be careful not to touch or disturb any linkage. get a good look of the top of the carb, take a good pic even. then see if the choke has tried to close. if not then look down the venturi and move the throttle 1/4 of its range while watching closely. if you see spray of fuel then you have not run the bowl dry. if you do not see a fuel spray then the fuel has gone somewhere or even not gotten the carb full.

the next thing to check can seem odd but it's a real thing. grab the carb by the top and try to wiggle and turn it in place. yfa carbs are a carb that screws to a baseplate which houses the butterfly. these are known for loosening up and creating an internal vacuum leak. sometimes masked by the choke being engaged yet shows up as a very lean start once warmed up and the choke is pulled off. if you notice it being loose at all you will need to remove the carb and tighten the screws from the bottom or by turning it over and spilling fuel. i hate fuel on me !! the screws are either a torx30 i think or a no. 3 phillips head depending on year and or whether it is new or a rebuild.

the other possibility is a vacuum leak not at the carb. this could be any number of small hoses or even a vacuum operated device like the heat/ ac system.