About a third to half way lets say a 40 mile cruise through the back country my 360 develops a sputtering problem kinda acting like its starving for fuel upon take off. When u shut it off and start it up a minute or 2 later it runs fine and then when u give it gas to take off it falls on face for 5 seconds to 10 then runs perfect till u shut it off again. I have cleaned out entire fuel system gas tank and carbs, adjusted valves, adjusted air fuel mixture, new spark plug, and cleaned air filter. ATV is stock. I am at a loss as to why its acting like this. If anybody can help i would appreciate it. Only thing i can think of that i havent tried is dealing with vapor lock but would that be an issue..?