There is always the risk of the numbers coming off. Even on the FX-3 my favorite 'safe' cleaner (409, a common household cleaner) took the orange off the "125" speed on the dial. The white remained underneath so I used a red marker to re-do it. Alcohol may take the numbers off.
I will say that when I got my first free FX-3 the ASA setting was frozen. I loosened it enough to change the setting with some 409 but it was never perfect again until taking the whole assembly apart and cleaning it.
From the KYPHOTO repair forum (proceed at your own risk):
[To remove the center disk from the shutter speed dial to remove it] A small sewing needle will sometimes work, but the last couple of FR-1's I have worked on required placing the tip of a soldering iron on the decorator disk. The heat will melt the glue BUT also marks the surface finish, and will probably require a bit of painting!