There is a oil pump under the clutch, some saws use plastic gears which can strip out. Make sure the oil hole in the bar matches up with the saws oiler, could be the wrong bar. Steve

pgtr: Steve is correct the Rancher 55 Model does have a gear driven oiler some models also had a oil plunger secondary oiler . The vent that you mentioned for this sytems is actually via two small holes that exit from the outer chassis casing under the bar adjuster cover . One hole is the oil exit the other is the atmospheric vent port. The oil exits the bottom hole and drips onto the bar chain groove and is dispersed over the bar . There is also a mechanical flow adjusting screw which controls the volume of oil . I would think that if you remove the bar and chain and carefuly clean away all sawdust from the saw casing and the bar inlet orifice and the bar chain groove you will see much better oiling . You could also turn out the oil adjuster screw a quarter turn . I have always found that using winter grade oil (thinner) that oil sytem clogging is much reduced . Bar Oil is a rather cheap owner expense compared to downtime so using a little more is not a big issue . . Best of luck with your repairs !