i just bought a k&n filter for my 01xr50 and was woundering what to do with the hose coming from the bottom end of the motor that use to go to the stock air box.
I did a search for k/n filter's for my son's xr-50,I do remember them saying that the k/n filter allow's too much air and motor need's rejetting and k/n get's excessively dirty quick and requires more often cleaning being it's out in the open without protection;those two point's stopped me from purchasing a k/n filter.
I believe K&N also makes a small filter for that hose also. It's been a while since I looked, but if memory serves right I saw it on E-Bay. Might look there and see if they still have one listed.