400ex just die not even stuttering nuttin but will restart

ok i have a 03 400ex that has a new piston in it and it ran fine for about a year if not more. well i was riding while ago the thing just totally died like it locked up on me well battery was weak so it wouldnt restart at the time. so i bought a new battery now the bike will start but when you hold it at kinda high rpm the thing will straight die almost like it locked up i mean it doesnt studder nothing. but it will start again! i hear kinda of a ticking sound so i check the valves those are good and its still has that sound. could the chain be getting loose? but i wouldnt think that would make it stop running like that.

Definatly sounds like a carb problem, I think maybe a dirty main jet, pop it out, spray some carb cleaner through the jet then spray through it with compressed air and see what happens.