I found the “2” will move by speed setting dial and the gear will push the “1” to change slow speed.
My S2’s problem is the “2” seems to tight and can’t restore to proper position.
Do you have any suggestion for fixing this part?
I don't think you would need to adjust 1 or 2 in the photo. Instead, I suggest moving the actual slow speed governor a little backwards/forwards/left/right.