My crude understanding of the UFM is that the oil enters at the middle of the bottom of the tank from the oil line that comes from the top of the rocker arms. The oil does not really enter the tank itself, but enters a steel oil line or tube that runs up to the oil filler spout. This oil line enters the little steel rectangle. This steel rectangle is really a splitter or diverter. The oil that enters the bottom of the tank spits out a hole in the steel rectangle. This is where the oil really enters the tank. In the top of the rectangle there is a screw (needle valve) with a spring. The screw or needle meters the oil that flows into a second tube at the bottom of the steel rectangle. This tube goes back to one of the two fittings on the rear of the UFM. In fact, it goes to the right hand side fitting that runs to the chain. By adjusting the needle in the opening of the oil tank you can adjust the amount of oil that is diverted to the chain. So, there is either oil in this tube because you have allowed it to flow through the needle valve, or the valve is closed and there is no oil flowing to the chain. Whatever oil does not go to the chain simply falls into the tank.
I think what Stumpy is saying is that of the two tubes in the UFM one is always carrying oil, the return, and the other,the chain oiler, is always carrying oil or it is closed. Neither can pass air as they are intended to be used. I suppose the chain oiler could be made to pass air, but its designed to be filled with oil so its location and the way it is designed would have to be changed. I have always thought that all of the UFM's (except the D) had the same plumbing.
David
I think what Stumpy is saying is that of the two tubes in the UFM one is always carrying oil, the return, and the other,the chain oiler, is always carrying oil or it is closed. Neither can pass air as they are intended to be used. I suppose the chain oiler could be made to pass air, but its designed to be filled with oil so its location and the way it is designed would have to be changed. I have always thought that all of the UFM's (except the D) had the same plumbing.
David