RD 400 Rear Master

[forexer]

1977 all stock bike w/ 3300 original miles that's been sitting for 28 years so it needs attention and I thought I'd start with the brakes.

I removed the rear master cylinder and took it all apart and cleaned it because the piston was froze and it would not move.

After the cleaning the piston moved smoothly and I thought all was good to go so I re-installed it and went to bleed the brakes but no fluid is coming out of the brake bleeder. So I assumed the caliper could be seized so my next thought was to remove the banjo bolt on rear caliper and see if fluid came out of the banjo bolt hole and it didn't so I'm wondering if maybe the master isn't building enough pressure and needs re-built even though everything looked good. ( Note: the tiny tiny hole in master is not plugged )

Your Thoughts  -

[forexer]

After further inspection it appears that the rear brake line is clogged internally.

Here's some questions -

1} do they sell new brake lines with the springs over them like the OEM brake lines because if so I can't seem to find them with springs that cover the entire length of the brake line. Yambits does sell them with springs but there not exactly the same. I'm trying to keep the bike looking original.

2} is it possible to remove the original spring off of the old brake line and install it onto a new brake line without damaging the spring I ask this because it doesn't look like the spring can stretch big enough to go over the fitting.

3} is there a tip / trick or a special tool to use when bending the metal tabs up when removing the old brake lines because I don't want to distort the metal tabs that are on the frame.

Thanks for help

[1976RD400C]

Those rear masters are very hard to bleed. You may have to pump and push fluid in the caliper bleeder up to the master and right through and up to the reservoir. As for the hose, if that's bad, you may just have to get a used one. I don't think you can get the spring off. The tabs, just carefully bend them with something that won't scratch the paint. They won't break.

[forexer]

Thanks for the reply 

The tabs ended up bending fairly easy as the clips to the frame seem to be a mild steel and I found that you can bend them just a little to allow the mounting rubbers to slip in and out.

I agree I may have no choice but to buy used brake lines because I'm unable to source OEM lines.

Lastly, I'm going to try your idea of pumping and pushing fluid through the caliper bleed back up into the reservoir.

[1976RD400C]

Auto parts stores sell these that will screw right on a quart bottle of brake fluid and then take that nozzle thing off and connect the hose to the bleeder, open bleeder and pump away. Do not push the brake petal as that will close off the little hole in the master. It always seems to work.

[jmendoza]

That widget is for filling the lower unit/gearcase of an outboard motor with oil.

The Mighty-vac is a better tool, and works great but requires a little patience, so here is the easy way to success:

Clear the brake line using compressed air, failing that, replace it. Make sure the rear caliper
piston is free. or rebuild the caliper. 

Fill the brake reservoir, pump the pedal a few times, attach the mighty-vac hose to the the caliper bleeder, open it and suck some fluid using the mighty-vac. Close the bleeder, top off the reservoir, and go have lunch or a beer. It takes about an hour for the fluid to slowly percolate through the system, and the air bubbles to rise, so the longer the better. Tap the caliper and line with a screwdriver handle to break the air bubbles free. Then you will find you get pressure really quickly and have good pedal with minimum bleeding.  I learned this the hard way, and have used this trick for years now.

HTH,
Jay