does anyone knows how to remove scratches from visor?

bro,
as far as I know, there is no solution to your query except to replace the shield itself (if the scratch is affecting your line of sight, reducing clarity). minor scratches are normal and almost invisible when the shield is in front of your face (especially shields with anti-scratch treatment). you may "try" to remove deep scratches but it'll affect your view from inside the helmet (i.e. warped view, blurry, scattered perception causing dizziness and confusion, etc.) makin it more hazardous to use the helmet itself. hope this helps...

O.T. - is this problem with your rf-900's shield?