The front brake rebuild not going well

I just finished rebuilding both front calipers. I installed new pads. I installed the calipers, connected the brake lines, and filled the master cylinder reservoir. I went through the bleeding process laid out in my Haynes manual. I bleed the lines until no air bubbles were present at the anti-dive bleed screws and caliper bleed screws. I even went back a few hours later and did it again. I can't get any force on the brake pads against the disks on either side. The brake lever just pulls all the way to the throttle grip. I am seeing no leaks. What can I do next? Do I have to replace the three copper washers on each side where the hoses connect to the caliper? Could I be getting air through there some how? Again no visible leaks. MS is original. Am I looking at a rebuild of that part? Please advise.

 

Just air in the system, tape a piece of plastic pipe to the nozzle of the vacuum cleaner & suck at the bleed nipple / s don't let the level in the res'get too low.

 

You may very well need to rebuild the Master Cylinder too; those parts don't last any longer than any of the other rubber bits in the system. Just like replacing the original lines (you did replace the old lines, right?) a master cylinder rebuild is part of a proper front brake refurb. Cheap, quick, easy insurance.

And yes, you should always replace the crush washers (or anneal them) but I doubt that's your issue or it would leak as well.

 

Hectic

The first question I would ask you is "did you have a decent lever before you rebuilt the calipers". If you did, then you can probably get that system bled to the point where you have a good brake lever again. From my experience that 750 system is a REAL bugger with those anti-dive units.

Wiz's suggestion should do the trick as long as you stick with it. Anything you can develop a vacuum with will work. I used a big syringe that you can get through an industrial supply house and just kept sucking. If you are trying the method in the Haynes of pumping the brake lever - forget it! It's not gonna happen! I was able to use that method on my 550 but it was a real PITA and that was with a single caliper and no anti-dives and it probably took me over an hour (including frequent pauses to give the wrist a rest).

However, bf's admonition to rebuild when in doubt should never be dismissed easily. You should never take short cuts where life or safety are concerned.

 

Yamaha said the original lines had a four year lifespan; and the caliper AND master cylinder seals a two year lifespan.

How old are they again?

And you still need to replace the lines if you didn't. Your life depends on this stuff, I'm not just being "overly cautious."

Ever think about what would happen if a front brake line "popped" during necessary hard braking?

It does and has happened.

 

The person who owned the motorcycle before me changed the caliper seals 6 years ago. The master cylinder has never been overhauled by him and the lines I think are originals. They had 1981 stamped on them. I am the third owner. When the calipers were frozen I did have a firm brake handle.

So it looks like a master cylinder kit and new brake lines. Can anyone give me a company that sells brake lines for this model and year bike? I know Yamaha does not carry them anymore. I checked.

If the cylinder of the MS is crapped up, how do you clean that out without damaging it? Are there any other parts of the MS I should replace during a rebuild or just use the kit? One other thing. I am using a synthetic DOT3 brake fluid. Does that make any difference?

Thanks for all your help.

 

HeckticHaze,

1. Where in upstate NY are you? I'm just south of Utica.

2. You can order all the parts you need from Len Chacal at xj4ever. Look in the upper right corner of each page. Click on his logo and it will take you right to his stuff. He is THE source, THE man, and THE most reliable trustworthy fellow you can imagine having around.

Dave Fox

 

1. I am North of Schenectady.
2. Going to get a hold of Chacal for some pricing on parts.

When I put new brake lines in should I install new Banjo bolts?

Thanks.

 

Bolts aren't required but washers are. Len has them to go with the lines at a reasonable price

 

Scotia? Ballston Spa? B.Spa is wher my mom is from............

dave

 

Scotia area.
Got a hold of Len. I have a MC rebuild kit, new brake lines, crush washers, union bolts, bleeder screws (mine are in rough shape), and some other items on order. Once I get the gear in i'll give it another shot. Thanks again everyone for your help.

 

I'll PM you later and give my email address. Next June plan on coming over for the carb clinic. Next June's will be #5. I'm ony about 1.5 hrs west of you.

dave

 

Hi, if you're changing the brake lines then it's worth considering braided lines, as these WILL give some much needed improvement to the standard 80's braking performance and feel.

 

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