I use a filter on my flight box and I don't have any problems with trash in the tank or engine.I still use the dubro refueler and have'nt seen the need for a felt clunk.I use a two line set-up and have no problems.Occasionally I do remove the carb and check for trash as a part of my routine mantinence.Before installing the inline filter on my flight box I would occasionally find trash in the carb screen.Since I installed the filter I have'nt had that problem anymore.Defueling is'nt a problem with this set-up.