Alright guys I really need some replies in this. Here's the story. I took my 2010 kx250f to the shop bcuz I could hear a small sound in the engine that I thought was the valves, the previous owner before me also said it needed new valves. Before I took it I rode it around the yard for about 5 mins and it ran fine but I could hear that noise. So I take it and they said the valves looked fine and the top end looked great but they went ahead an put the new valves in for me anyway?? Anyway, they call me an ask me if I had noticed any other problems with the bike. I said no, why. They said that they out the new valves in it and now the bike will start and once warmed up makes a loud noise in the engine then after bout 10 mins the bike will cut off. They also said it won't stay running in low idle. What could be the problem??