my sister put a vinyl hatchet man on her car and its just primer but it stuck fine just dont peel it off cause it will take the paint with it
or you can use my method paint the whole peice the color you want the graphics to be then stick the the decal on and flat black over it then remove the decal if you look hard enough you can find a clear that is a matt finish so you can seal the paint without having the shine of gloss
did they come with a little plastic spacer?
cause they did the same thing to me but instead of returning them i just wrapped a layer or two of black tape around the clutch side no glue needed and used the spacer to take up the slack in the throttle side if that is the case for you you're going to need to shave the inside of the kill switch housing down some so the throttle wont stick
I would wet sand the side covers starting with 120 grit and working up to 1000 grit, primer the covers with sandable primer and resand with a green scotch pad just enough to take he sheen off, then paint them flat black