'81 Interstate rear brakes

[GTC@MSAC]

I had to overhaul my Rear MC when I 1st got it 3 years ago, all the brakes, in fact. Can't remember now where I got everything, but I did, as well as new caliper pistons, and Front MC reservoir.

 

[D-50Dave]

Finally made some forward progress. :yahoo: Assembled the MC with plenty of fluid, (found that the bulb that is used in home ear wax removal kits works great), mounted and still couldn't get any draw by pumping so I put a small amount of air pressure down the reservoir hose. Then pumping started to draw in fluid. I had learned only one way to bleed brakes: 3 or 4 pumps, hold, break the bleeder and tighten, repeat. After several dozen cycles, still soft, but applying pressure well to the disc. Asked a friend who is a professional auto mechanic and he said try: open bleeder, pump and hold, close bleeder, release. He's offered up his vacuum system if that fails. Just great to be moving forward again. arty: I'm not much of a mechanic, so what many of you do that looks so easy is often a struggle for me.

 

[mcgovern61]

One last item about bleeding '81 brakes. The bleed screw in the caliper is not at the top of the caliper. As a result, all of the bleeding in the world will not get the last air bubble out. Disconnect the two caliper bolts, tilt the caliper upward so that the bleed screw is the highest point (while keeping the caliper on the rotor) and then do a final bleed.

Also, while bleeding rear brakes, be sure the master is topped every time you pull fluid. These reservoirs are kinda funny that way.

 

[dan filipi]

The first time I used a vacuum bleeder, I kicked myself for not getting one earlier in life!
The kit is pretty inexpensive from Harbor Freight. ($25, similar online)

 

[D-50Dave]

Great tip, Gerry. I'll make sure I do that. :good: I don't let the reservoir get much below the "Low" line before topping up.

 

[mcgovern61]

It is best not to let it get below the middle between the lines. That is because the rubber cap inside has an expandable cone that pulls down as the brake fluid is let out from normal wear on pads. It helps keep a small vacuum on the line. If you get below the low line, you have exceeded the length of the cone and it can allow air in again. The rear brake system is pretty small and everything matters!

 

[D-50Dave]

During the bleeding process, I have been leaving the cap off. Is that a problem? When finished, I would fill to top line.

 

[pidjones]

During the bleeding process, I have been leaving the cap off. Is that a problem? When finished, I would fill to top line.

Just be careful it doesn't spit back when pumping. Some GLs have nothing above the relief port, and a little geyser of fluid comes out each stroke. Most have something over it, but some don't.

 

[D-50Dave]

There is no spitting, so I should be ok.

 

[D-50Dave]

So, I wrapped up the bike this afternoon. The alternate bleeding method improved it enough for me to button it up. Not quite as tight as it was, but full brake before the bottom; just a bit more travel. Thank you to all who have supported me and my un-smart hands.
I wanted to pass along a mod that was buried in the bike when I bought it in October 1989. It came with the Markland floor boards and the brake pedal was in the perfect position for them. I remember a while ago, another member mentioned that there was substantial interference with the pedal and floor boards when he went to install it, but I didn't give it much thought at the time. When I ordered a rebuild kit from BrakeCrafters, the rod was an inch shorter the the rod that came out. I got on the phone with a very helpful gentleman, with a british accent, who dug around and found that the rebuild kit for a 1987-88 Yamha FZR1000 had the rod that was on my bike.

From left to right: Stock rod, old rod, FZR rod.

How my pedal is oriented with the FZR rod.