On a 701 (I'm pretty sure the 650's are more or less the same), the line from the pump comes in and goes to the exh manifold. The water goes through the exh manifold into the cylinders and then up and out the head through two lines. One is small and off the front side of the head and it goes to a small port on the pipe chamber. The larger one comes off the rear of the head and goes to the elbow of the exh that is just after the manifold. I think this is the one you are dealing with but it is hard to tell from the pics.