Rear master cylinder not building pressure?

Hello all,

I have recently bought a 78 KZ1000A2 from a friend of mine. It wasnt running but I figured for 150 bucks I could get it running for cheap. The bike was all there and after some new plugs, she fired up!

I've bought a few things from z1enterprise.com for the carbs and ignition.

One thing i didn't buy was anything for the brakes. Both front and rear calipers were rebuilt. The front works flawlessly. The rear on the other hand has been a pain in the rear. Literally! The rear master cylinder would not build line pressure and the piston in the master was stuck at the top. I rebuilt the master and still didn't work. The piston was slow returning to the bottom of the housing and built zero line pressure. I took the line off the master cylinder and it didn't even push any fluid out of the port.

Any ideas on how to fix. I know they sell a rebuild kit but am nervous that I will run into the same problem. My bore pretty good in the master. Is there any aftermarket/custom mounted master that works? Anything that anyone has tried/done that has worked?

Thanks!

I also just acquired the same model and I just got my rear master cylinder working apparently for the first in a very long time, judging from the amount of crud in the system.

Mine wouldn't build pressure at first either. So I took the banjo bolt out of the top and held a finger over the hole and pumped the b rake. It squirted fluid then. It seems the system needs back pressure to work properly.

This was after I had already disassembled the cylinder and cleaned all the components with soap and water then used compressed air to clear all water and be sure the tiny orifices were open.