Please help! Out riding bike for maybe 10 miles at 60mph, everything feels and sounds right then it starts to die. I knew I had plenty of gas, but tried switching to reserve, no change. Went back to main tank. Can open the throttle just a little bit and she will keep going, any more than a 1/4 turn of throttle and she shuts down. I am figuring fuel filter or carb. Please help.