Mine came with an aftermarket master cylinder attached, but had the original. Cleaned the reservoir and bore. Ordered a new rebuild kit, and installed.
Locking up is usually caused by the tiny hole (some call it spluge hole) in the MC. I clean them with a high "E" electric guitar string chucked
Good luck with your 78. Keep us posted with updates on your project.
I moved your post into the correct forum. Have you checked fuses? power to and out of the switches? Power to the bulb with the brake lever/pedal
I had the same problem. Replacing the bulb fixed it.
Tail lights on but no break light
Bloody Mary Today, 01:20 PM