At that point, it becomes an experimental situation. What is happening is that when you "tension" the blade, it is pulling that wedge toward you and forcing the upper arm up to apply tension. So, essentially, when you back off the tension from 5 to 3, you are "lenthening" the rod. So if that makes the noise go away, I'd turn the rod out a thread or so. That way, you can have the tension set at 5 but in actuality, it is at about 3. Not sure that is a good thing as you need to be able to have high tension is some cases. What I'd try to do is figure out why, when set at 5, it is making noise. I think the noise is coming from the upper connecting rod, as they call it, contacting the underside of that cover. So, you might have to take some more off of it. I'm pretty sure that is where the knocking is coming from and it only happens at high speed. You are on the right track though. Once you are done, you will have a very good understanding of how the mechanism works. I'm not sure why it doesn't happen to the bottom connecting rod. Probably because there is nothing there for it to bang against. If you could nail down exactly where the upper con rod is hitting that cover, you could probably file it down a bit. Instead of the cover. Try taking more off the cover as that's the easiest spot. I had to really take a bunch off of mine. If I still had the saw, I'd take a pic for you.