I just bought an 82 CB750C. The second time I ride it, it started smoking from the front of the engine. When I investigated, I found a small valve high on the front of the engine. Oil seems to be coming out of this valve and running down the front of the engine. This is causing the smoke. I checked th oil this morning and there is not enough left to read on the dip stick. Why is the oil coming out and how do I stop it?