05 450fse won?t stay running.

[Dirtnasty]

I have a 2005 450 fse. The bike was running just fine and I decided to go and screw it up!! It has 3,000 miles and always had a hard time starting when cold so I decided to check the valves. They were barley off but I adjusted them anyways. I put it all back together and started it. It runs for a minute then gets hot and shuts off. I took it into a local bike shop and have paid them $300 and it?s still is doing the exact same thing. They have had the bike for 4 months and they can?t figure out what?s wrong. I?m hoping someone on here has an idea what I should check. Thanks in advance.