I didn’t realize that it needed specific bore. I just used a stock master cylinder. Does a MC need to be bled and if so, how?
You can and probably should fill and bleed it on a bench before installing. Clamp the flange in a vice securely with the MC level. Put a reservoir on top—get the kind that just plugs into both soft leads. Plug in the senders and block all the ports except the ports in each that will be used to feed fluid to the brakes. Screw short brake lines with fittings into those, curl the lines up and feed them back into the top of the reservoir.
Now fill the reservoir with new brake fluid from an unopened can.
Gently push in the plunger using a metal rod with a rounded tip, or a big phillips screwdriver, being careful not to slip off the indent and mess up the seal.
In a few rounds you'll be pumping fluid through the unit. You'll see it's not blowing air.
If you can, suck the fluid out of the reservoir before unplugging it. If you can't do that, just take the whole thing out of the vice and pull the res off over a trash can.
Plug the top holes to keep the fluid in. Be quick when you install the MC.
You still have to bleed the system but it should be less arduous.