Hello,
How are front brake calipers reinstalled? Is there a tool that holds the brake pads back, or is it necessary to open the bleeder?
Thanks

Opening the bleeder may help, but if you can push the pistons in easily, it won't make much difference. If the pistons go in firmly, it will.
An old trick is to use a small piece of sheetmetal to use as a guide to slip the pads into place by holding the pistions back.

Ken Styer

Try Eclers,
they have these clips that go over the piston to hold them in , I think the price was 15$, I haven't tried them yet , but it's alot easier then bleeding those brakes.

bought my clips from MA. made the job very easy.