fuel system

[yambutt]

I had a minor problem riding my 1992 fj today, it started hesitating while I had a little less then a half tank of fuel, switched to reserve and ran fine, so then I stopped to fill the tank and ran the tank on normal, and in about ten miles it started to hesitate again, so switched back to reserve and ran beautiful for the remainder of the trip which was around 150 miles on reserve, so is there a filter I need to clean in the petcock, I changed the fuel filter around 4000 miles ago, and how does it go from normal to reserve when pressing the switch.....thanks