Ironhead brakes...*sigh*

I only rode my bike once before stripping it down and the brakes were SHlT!

It has a non-oem master cylinder (v-twin) and I think maybe its not the right bore for the twin disc brakes (79 Sportster). Does this sounds likely? I know the brakes on these things are rubbish but as it is its dangerous... Dan (fevah) had a ride and overshot my driveway when he came back, and he wasnt going fast, it just wouldn't stop haha

If I was to buy another master cylinder what bore should I get?

Cheers

You could buy another master cylinder, just get an aftermarket replacement for an Ironhead, of a good brand.
But it could also be poor performance of your calipers - could be sticky. Could take them apart & clean them & re kit them.
Also pads could be contaminated, which would also cause this.
Personally, if you like the bike & are gonna keep it, I would get a PM (Performance machine) master cylinder & PM calipers with multiple pots (4 or 6 pot) & maybe even new rotors. Certainly those PM calipers would make a big difference (with a matching master cylinder, or probably even with an OEM master cylinder?-someone correct me if Im wrong) & they probably have a bolt on set for ironheads.
That's my thinking but you'd better ask Doug aka Pan/Shovel