Yep, needle & seat or center carb gasket. I am having the same problem with the carb. loosing its supply of gas after a week or two. But if I start it every 3 days or so, it starts instantly.
57 GMC LCF 370 55 John Deere 40-W 59 John Deere 430-W 2000 GMC 4x4 56 John Deere 420-W Pix on Photobucket