Did you repair or replace the chain Or Is the chain new or second hand? In my old chain driven motorcycle, alternating tension and slack meant that the chain had been stretched unevenly and should be replaced... I will admit I haven't got any experience with Pathy timing chains...so I can't say whether it's normal or not - but If I saw that, I'd be looking for second opinions too...
14.78 MPG 60% in town and 40% mountain highways. Manual transmission. I always feel it should do better than that and occasionally it does when I'm on the highway more. So I'm glad to see that in this forum thread, at least, my mileage is fairly typical.