The v-twin bobber/chopper rigid bikes tend to stop pretty well with just a rear brake. I don't know if it's the lower center of gravity, or what. I was used to using a lot more rear brake on my rigid bobber than the front...until one day...the cap popped off my oil tank and oil got all over the back of the bike. That means no rear brake. The first time I went to stop without it was quite a surprise, to say the least. When I managed to pull over I initially though the caliper was leaking, until I lifted the seat and found the oil cap not seated. It was a rubber stopper sort of thing that was just worn out and a loose fit.
I made it to an auto parts store and bought a couple of cans of brake clean and some paper towels. I cleaned the back of the bike up as good as I could, but it had no effect on the lack of brakes. The pads were soaked with oil. I'm glad I had the front brakes, but they weren't as effective as the rear brakes. I was on a long ride too and at least 150 miles from home. I made it back safely. The bike got a thorough cleaning new pads and a new oil cap.