[DW31S]

I know you say that it has not tampered with, but are you 110% sure the pointer is original? The posts about the timing chain, balancer ring, and advance springs are all noteworthy, too. Nylon gears are a time bomb, they are gonna go, just a matter of when. You can't tune by the old service manual; conditions now are not the same. Cheap gas then was better than our good stuff now. Just make sure you try changing one thing at a time. If you make all the adjustments at once, you won't know what did or did not work. Try the old "all in by 3500rpm" and see what happens....that will get you in the ballpark.