The most likely reason is that one or more of your flexible brake hoses are collapsing internally. This is a very common problem on OEM brake hoses across all bike brands. It usually happens to the hoses that flex the most during riding, however it can occur on any of them.

This is an excellent reason and time to convert to "stainless steel" brake hoses. They have a PTFE ("teflon") inner hose that isn't attacked by the brake fluid and they also have a stainless steel braid to support the high pressures exerted during stopping. Because they don't expand with pressure during braking, using these type hoses will increase your braking efficiency a tremendous amount. It's no exaggeration to say it will feel like you have double the braking power.

Because they cost about the same as the OEM hoses, IMHO buying the OEM hoses is really throwing your money away.

Hope this helps.

An update. So the front hole was plugged and not open to the piston below. I opened it up. This allowed the brakes to "release" but still spongy. Replaced all the hard lines and hoses. Brakes started to work at about half pull on the lever but would just about go to grip. Found that the right caliper was leaking in between the halves. Rebuilt it with the kit. I will say it was difficult to get a seal, you need to tighten this like a head to the block. It took four tries to get it to seal. Now I have brakes at about 1/3 and full lock at 1/2 pull. I can probably only pull the lever back to 3/4. My guess is that I still have a little more air in there and will work to get it out in coming days. I did reroute the over tire brake line outside the fender, the under the fender just made me nervous.

This weekend is a shock rebuild with progressive springs, new fork seals and new bellows for the fairing. Then I shall be tearing up the roads of north Florida! My reason for the springs is that I feel the bike dive about 2 inches under braking and even some movement with the wind against the fairing. The fork seals are leaking so I thought I would do a full update whilst it was apart. Some peace of mind with new innards going in!

Courtney
#16121

An update. So the front hole was plugged and not open to the piston below. I opened it up. This allowed the brakes to "release" but still spongy. Replaced all the hard lines and hoses. Brakes started to work at about half pull on the lever but would just about go to grip. Found that the right caliper was leaking in between the halves. Rebuilt it with the kit. I will say it was difficult to get a seal, you need to tighten this like a head to the block. It took four tries to get it to seal. Now I have brakes at about 1/3 and full lock at 1/2 pull. I can probably only pull the lever back to 3/4. My guess is that I still have a little more air in there and will work to get it out in coming days. I did reroute the over tire brake line outside the fender, the under the fender just made me nervous.

• Sounds as if you still have lots of air in the system. The natural place for air to accumulate is at the top of the U-tube connecting the 2 calipers. I find pushing fluid up from the caliper to be a better plan of attack than traditional m/c-to-caliper "bleeding". Bleeding simply doesn't move enough volume of fluid fast enough to chase out tiny air bubbles in that area. If you installed aftermarket "stainless" brake hoses, then the lever should be rock hard.

• Damage to the U-tube under the fender is simply an unfounded fear. The bike is 30 years old. If it hasn't sprung a leak so far, then what's it going to do now ?

• Several of the "stainless" flexible hose makers simply convert that layout over to dual, independent lines going back to the m/c. There's a lot to say for that design as it removes places for air bubbles to collect and hide. For the average rider it's a better design becasue the m/c then becomes the highest place in the system. In other words, no place for air entrapment. In that way the system becomes self-bleeding, and thus self-maintaining.

Got most of the air out, still gonna try one more bleeding but this time, with the front wheel out and kinda holding the calipers sideways. I am confident that the remaining air is in the "over the wheel" part of the line. Just have not decided which way to turn them to either go out the top or out the bleeder, we shall what space allows! I will upgrade to the stainless lines but want to collect all the part prior to doing that.

thanks all the advice. It is really helpful and gives me a different way to thinking about these things. The Clymer manual tends to over simplify some of these issues.

I went an bought a new pump oil can and filled it with brake fluid. Then a 2" section of battery hose was used to connect the can to the bleed nipple. That's how I pumped fluid up to the m/c. That will chase the air out.

You want the bars turned so that air can rise from the hose into the m/c reservoir. The hose needs to be lower so that air can naturally make its way out as it floats up.

Sometimes if you'll simply pump the brake lever slowly and methodically you'll see very tiny air bubbles rise in the m/c reservoir. Do this while tapping on the banjo fittings with a screwdriver handle.

Basically the exact method that I dreamed up too! I am using a 100ml syringe. It dawned on me as I read one your other comments that the brake lever was only going to deliver a couple of ml of fluid into the system and that would not be enough to run fluid all the way from one caliper to the other. So any air trapped in the loop over the wheel would get pushed a little further down the line then return right back to the top of the loop. I may try to pull on the fluid from the bleed valve too.

I am going to investigate the steel lines in the very near future but will save that one for a time when I can procure a new bleed screw for the other caliper too. Then I will have a T up in the frame area and run two flexible lines all the way to the calipers.

I cannot express my thanks enough for the advice I have found on this site. If nothing else it allows me to start thinking of solutions. I mean part of the fun is working on these bikes, well, at least for me it is. If we ever meet up (and I am sure we will), I owe a beverage of your choice!

Courtney
#16121

You are exactly correct in your thinking.

The factory gets away with the loop over the wheel simply becasue they push fluid in at such a pace that the bubbles don't have time to return to the system high spots. That's great for fast manufacturing, but creates a royal headache for the home mechanic.

For home service you may want to push 4 or 5cc's of fluid from the brake m/c down to the caliper in a more "traditional" bleeding. If so, then re-designing the hose layout might make the most sense. Especially when you consider that the simplest system is to run a flexible hose from each caliper, all the way back to the m/c. With a 2 hose design you avoid the cost of the T connector, extra bits, and 3 hoses. You simply need the double length banjo bolt to connect them up at the m/c.

Download the Fragola Performance Systems catalog and take a look at their AN-3 pre-made and special order brake lines. That's what I'm using on all my Airheads.

Cheers

Did the bleed with my Syringe from the bottom up. I sucked out most of the fluid from the MC and added a touch more from my container. I attached everything and really opened up the bleeder (half to 2/3 turn). I did a hard and fast push with the MC at the highest point. I would say I pushed 15 to 20 ml of fluid up the system. I then closed up the bottom end and went up top to "jiggle" the lever (short strokes while tapping the banjo fitting lightly with a screwdriver handle). More a vibration effect. A few good sized bubbles emerged and now I have brakes starting at about 1/8 pull or so. Basically, as good as it is gonna get!

Going to ride it like this for awhile and then work on the stainless lines once I decide on the double banjo versus the splitter. Right now I am looking forward to putting on some miles; speaking of which, I think I will hit the road this afternoon so as the weather in Fl seems to be behaving today. Probably gonna lose the entire weekend to rain.

Courtney
#16121

Hey, congrats !

As you ride this week, at the rest stops... lean the bike slightly to the left (making the m/c the highest point) and give several long, SLOW, squeezes to that lever. I bet the heat will chase some more air out and the lever may get even better.

You are going to kick yourself when you finally install the stainless braided brake hoses. You'll wonder why you waited so long. It will make your front brake feel like it's got some sort of power booster installed.

Be sure and fit some modern brake pads. 40 year old pads can't be that good at stopping.

Good advice thanks. I know that the new lines will be a game changer but for now I shall revel in the fact that I solved the problem and did not do it with my wallet! It really is satisfying to figure these things out. I had to rebuild one caliper in this ordeal and now I know exactly how they work.

I had to rebuild one caliper in this ordeal and now I know exactly how they work.

And that's why Club Cannon #6 is so important. If you don't do it yourself, then you are a slave to the one person in town that will do it. And as happens so many times, "bewildering" items, like the operation and care of a brake caliper, become "stone ax simple" once you take the time to open them up and take a look.

Congrats on the repair AND the expansion of your knowledge and understanding.