Hey there, i got a motor i have been working on for a while. Finally got it to run a bit and it dies once the carb runs out of fuel. It does run if i set the tank above the motor or if i press the primer button (two line fuel line btw). I have rebuilt the carb and the tank and can't find any air leaks in the lines either. The tank seems absolutely solid because when i prime it the button gets super stiff. What's next? Take a look at the check valves coming out of the crankcase? Appreciate your help.