I ran into this when swapping a 1997 FLHT front end on my 1978 FXS. The old style master cylinder will work with a banjo type fitting. My new caliper uses a banjo style brake line. Unfortunately the old master cylinder does not. But guess what? It can. I was looking at all kinds of adapters, fittings and possibly a custom made hose. I decided to just try this. I pulled the old line off along with the adapter fitting in the MC. A banjo bolt screwed right in but was too long. Found a thick stainless steel machined washer in my junk box and added a third sealing washer. Problem solved. And no leaks!

 

I just used a braided banjo top hose from my 06 Ultra on my 80 Shovelhead and it bolted up just fine. I only needed 2 crush washers. So left the 2 lines from the tee manifold to the calipers alone. I eventually will change the sliders so I can run Brembos up front.

 

The '80 uses the same mc as my '78? The bolt I had didn't feel like it wanted to go in all the way and I didn't want to force it too hard, hence the spacer washer. I wonder if the bolt you used is shorter than the one I used? I used a bolt from a caliper. Maybe one from a mc is shorter? Anyway, I am syre happy it worked out. I hated to think about ugly adapters or compression fittings. I am not sure what my hose came from but it was at least 2006 or newer.

 

your's looks chromed, so it's probably not the OEM master cylinder. Here's mine with the compression flange, it got in the way of viewing the head temp guage is why I wanted to change mine.

 

No it's not the oem mc but is built exactly the same. I didn't think it would take the banjo bolt at first. I figured that the adapter that originally screwed into the mc was npt, but obviously it is a straight thread the same as the bolt. I had just never heard of anyone changing to the banjo fitting on the older style master cylinders. It sure made my day when it fit. I just wonder why mine was reluctant to screw in all the way. It might, I just didn't put a wrench on it for fear of screwing up something. It works well with the spacer I used though so all is well in Shovelhead land!!