150cc GY6 scooter lost top speed

[Battercake]

For a couple months now, I've been trying to pin down why my scooter, which would usually go up to 62 MPH if I so desired, will usually only go 51 now. This problem began at the same time I had to replace the carburetor diaphragm, so naturally the assumption was that something was affected by that, and a wild goose chase ensued. But this week I had the cover off the CVT and noticed grooves in the variator pulley. I wouldn't have been concerned had they been near the top, but these grooves are only about two-thirds of the way up on the pulley.

I assume my next step is gonna be to remove the variator pulley and see what's going on behind it. Any advice is appreciated!