Had a really good first ride today up in the mountains. But on the way home, with about 100 miles of fuel left the bike started to surge pretty bad. Completely off/on for fractions of a second. Lurching hard and then would be ok for a bit. I got home and pulled the right side cover and verified that the petcock was open. The left side was easy. So with both petcocks open do any of you have any insight on this? Bike was perfect all day until I was lower on fuel.