dieing out

[kfx400rider03]

well i went out to breezewood this past weekend and got 7 laps in before my quad died. it turned over really slow(battery is not dead) then would not turn over. towed it back to the truck and tore the valve cover off to check timing and it was good put it back together and it turned over started and does not idle all the time. and when you give it gas it does not cut out or anything but it will just randomly die. like i had it running and held it at 1/4 throttle and it did not cut out or sputter but after 5 seconds it just shut off like as if i turned the key off. after that i did not wanna run it any more and cause any further damage.
mod list is in my sig.
any ideas?
thanks