I tried the so called wheelsmith spring on my 490. It didn't work properly. It was like the coils were binding up and running out of movement. I have also seen a post saying that when fitting the coil spring you should leave the locking plate out, just use locktite. That makes sense the extra 1.5 mm might just make a difference. I haven't tried it yet, but polishing everything does also seem like something worth considering.