I have a 2002 yamaha kodiak 400, two weeks ago i was atving in my feilds and then it died out, it just stoped working it would idle but one i pressed the gas in it wouldnt go and it would try and die out So then I brought it to the dealer and they rebuilt the carb, and replaced the petcock valve, Yesterday I went out on the trails ( Got it back yesterday) And it was running like new on my way back I was going full speed and It just died again and i had to drive back home going 5kph or it would die out.

I cleaned the airfilter, changed the spark plug and brought it to the dealer and they replaced the petcock valve and rebuilt the carb. what else could it be??