I have a hose with K&N filter there because I run a K&N filter on my carb. I like to think that they run the crankcase breather into the airbox because they don't want dirt to get sucked in in the case of back pressure. If I was you I would put a hose and filter on it. I also run a filter on my head (valve cover) breather. A lot of people don't because there is not a lot of back pressure, but I run one to be safe. XR/CRF50's are bullet proof and I like to keep them that way. I guess you could run a hose off your dipstick, but I think it would be a waste of energy. There is already a breather on the crank. It's a 50 and there is no way that it could build that much pressure. If you want to go ahead, but run a filter if you do. I just don't have that much time on my hands.