Just to satisfy myself on this issue, I pulled up the pick of an LR4 timing chain kit. Assuming the pic is correct, the crank sprocket has 19 teeth which I believe requires a cam sprocket with 38 teeth (to keep the 2:1 ratio). The timing chain appears to have 70 links. So, the cam and crank sprockets should be in the same position every 2 rotations, but the chain will only have moved 38 links. Furthermore, when the chain is back in its original position (3.68+ turns of the crank), the cam and crank sprockets will not be in the original position. Eventually, everything will line up again - but it will be many, many revolutions later if the numbers I have above are correct.