I have some syringes and a bleed fitting for the master cylinder. Does anyone know what size of tubing to use?

one that fits, its not vital.

i think mine is windscreen washer hose.

I use air pump tubing available from any pet or aquatics shop, make sure you cable tie it onto the bleed nipple and the syringe for extra security as theres nothing worse than a jet of brake fluid flying all over your prescious steed and floor 😯

Can I use 5.1 dot brake fluid on Hayes brakes? It says only use 3 or 4 dot fluid. Any reason why? I thought the only difference was higher boiling points.

I just used the brake oil that was in my garage and think it was 5.1-no ill effects apart from over filling the system so some of those nasty after market oversize cheap brake pads didnt fit without dragging so ended up having to loose some fluid out the system.
I used windscreen washer hose, nice tight fit too so no danger of pressure problems (thats always eased anyway by opening the bleed nipple quarter turn more than you think you need-you shouldnt have to be pressing hard on the syringe plunger!)
Just make sure any spillage on your levers is wiped off well as it eats the paint finish on it!!!