Special pins are available to hold the backlash springs in position, or you could make your own. It's easiest to do before removing the cams. You can put a 6mm diameter steel pin, approx. an inch long, in a a drill, and use a file to turn down one end to 4mm. You'll need two of these. Very easy to do.
Insert then in the holes in the cam gears and you're good to go.
