Took my 02' xr650r up to Vermont this weekend for some nice riding. First off I have a 172main, 68s pilot, B53 needle in the 3rd clip with HRC tip and all other restrictions removed. We rode at 850feet/ASL too. The bike runs excellent all the time. Well we go out on Saturday morning to get them fired up, took a while, damn cold. Well the bike ran mint for most of the day, then we started on another trail and it was gurgling and sputtering down low but was fine when it hit the main jet. I stopped and the bike would not idle to save it's life. I tried messing with the idle and fuel screw to no avail. What's the deal, it ran fine all day and then just ran like crap. I got it home last night and it did the same thing so I know it's not an elevation change issue. I haven't had time to check yet but I'm guessing dirt in pilot jet, vents tubes blocked, bad gas??? Any help?