So, have a 1977 R100 that I bought, have been ridding it for weeks, on and off. Oil light comes on the other day and I check the oil, none on the stick. CRAP. Put exactly to the line this morning, ride it 50-60 miles and just checked it, its lost about 1/4 of the level. I made several conscious efforts to look back and watch the exhaust and I never say any smoke, either on the acceleration or deceleration. It has very low miles and was a resurrection project that someone else did. Where is all of this oil going? There is about a quarter size drop of oil in the back right region of the pan, but not nearly that much oil. I would say rings locked but how so without smoking? O-ring on the pump?