Topic: Another sticky front brake thread - solved

[TwoTired]

There was a small white nylon ring with the piston-side pad. Should that be installed with the pad?

Yes

I have been driving around with the lever pulled and i can still drive in 1.st gear with the lever pulled all the way to the handle.

Absolutly sure there is no air in the system. Mc still not leaking and no other leaks can be seen on the system.

There are a limited number of causes to the symptom you describe.
It is very hard to believe you don't still have air inside the hydraulic system as that is number two on the list.
Number one would be leaks.
Number three would be non-rigid hydraulic lines.
Number four would be low friction disc pads.
Number five is a compressible liquid in the system.  What are you using for brake fluid?  Is it purple?

Have you read the front brake caliper rebuild article in the FAQ?

The pads are porous.  If they have been contaminated, heating the pad will bring grease, oil, etc. to the surface to reduce friction.
They also take much longer to seat and make full contact with the rotor when lubricated.

The nylon washer serves two functions.
1) It helps keep the caliper side pad wear even.
2) It softens initial engagement so the brake has less initial grab.  (this makes them feel more like drum brakes.)

I can't help but think you are overlooking something.  Maybe it is time to seek professional help?

Best of luck,

[jensk]

I am about to reach the same conclusion as you are - I need profesional help on this. I think I have read the brake faq, the original Hondsa workshop manual, the Haynes and the Clymer book.

I have mounted a 1 meter piece of tubing on the bleed screw - tied the other end to the ceiling and have had the reservoir and the bleed screw opened for 48 hours to get air out of the system. Brakefluid leveled weel between the tubve and the reservoir.

My brakefluid is from a new bought bottle (seal unbroken) Dot3 fluid. The fluid is clear yellow'ish.

I did discover several cracks in the lower rubber brakeline so today I was at several dealers to get a new braided lower brakeline. None of them could make one needed because the lower joint to the copper brake pipe was of a type not used/accessible anymore in Denmark.

They offered to cut the copper pipe and mount a new joint on the brakepipe that would fix current brakeline fittings. I will bring the caliber and brakeline tuesday and let them do this conversion and at the same time get a braided lower brakeline.

On of them told me that the lame braking also could be a result of have a disc that have been warmed to much for to long. He suggested to get a new disc but i don't know if he is just getting me to buy things i don't need. How do i determine if the disc is worm out by to much heat for to long. The disc is not worn to this according ot the manual.

[kslrr]

Unless your disk shows definite signs of excessive wear or has deep groves, you do not need a new one.  Just have it dressed up a bit to roughen the surface.

[OldSchool_IsCool]

The disk may be stamped with its minimum thickness.  Make sure it has plenty of meat left by making sure it's thicker then the minimum specification.

[TwoTired]

I am about to reach the same conclusion as you are - I need professional help on this. I think I have read the brake faq, the original Hondsa workshop manual, the Haynes and the Clymer book.

I can imagine you are getting pretty frustrated with this. My condolences. I can only recommend perseverance.

I did discover several cracks in the lower rubber brakeline so today I was at several dealers to get a new braided lower brakeline. None of them could make one needed because the lower joint to the copper brake pipe was of a type not used/accessible anymore in Denmark.

Was the "part not available" comment made by the same person who recommended replacing your disc?
Yes, the "conic reverser" you need is not easy to find.  My Honda dealer doesn't have them.  But, my local M/C repair shop has them, and they are still available!  I can pop one in the mail for you if you can stand the delivery wait.

One of them told me that the lame braking also could be a result of have a disc that have been warmed to much for to long. He suggested to get a new disc but i don't know if he is just getting me to buy things i don't need.

I recommend you glaze your eyes and allow your mind to wander when this person speaks to you again.  He may have an illness that involves absorption of bovine waste.  Beware, you don't catch that disease by listening too intently.
If this is your "professional help", I withdraw my previous comment on the need.

It sounds like you lower line is a definite problem that needs correction.
But, on the subject of brake bleeding...
Try to imagine a fluid vessel with rising bubbles in it.  If the vessel is irregular, the bubbles may be blocked from rising to the surface.  Look at your brake system in the same way.  Imagine a bubble in the caliper as it rises toward the master cylinder.  Are there any ledges or coils of hose where it can linger?  These trap air to prevent proper bleeding of the system.  Reposition components, handlebars or the entire bike so that internal bubbles have an unobstructed ramp to the master cylinder bleed hole.  With the stock SOHC4 single caliper brake and master, I can bleed the brakes overnight without using the caliper bleed nipple at all.  All the air escapes through the master cylinder bleed hole when the machine is positioned properly.

Best of luck!

[paulages]

Try to imagine a fluid vessel with rising bubbles in it.  If the vessel is irregular, the bubbles may be blocked from rising to the surface.  Look at your brake system in the same way.  Imagine a bubble in the caliper as it rises toward the master cylinder.  Are there any ledges or coils of hose where it can linger?  These trap air to prevent proper bleeding of the system.  Reposition components, handlebars or the entire bike so that internal bubbles have an unobstructed ramp to the master cylinder bleed hole.  With the stock SOHC4 single caliper brake and master, I can bleed the brakes overnight without using the caliper bleed nipple at all.  All the air escapes through the master cylinder bleed hole when the machine is positioned properly.

jensk- this is why i was suggesting not only bench bleeding the master cylinder, but actually bleeding the junction as well. i've seen air get trapped there, with a line just like yours sounds. one time, was quite dramatic- upon bleeding at the splitter (this one was a '77 750F with the dual-line splitter at the lower triple tree), a loud hiss of air was released, and the brakes became immediately harder. these systems can be quite difficult to completely bleed.

on top of this, i suggest the following: lightly jiggle the lever (not all the way in), while tapping around on the line the entire way up to try and dislodge any trapped bubbles. if you get it to a point of safe riding at all, ride around jiggling the lever in the same way. the road vibrations will help work them up, and this motion with the lever is all needed to allow them into the reservoir.

i have two disks and calipers on my '76 550F, with the stock master cylinder (but do have SS braided lines). at first, a dual-capacity master cylinder was on my short list, but doing these things ended up leaving me with great braking, and a pretty stiff lever even with the stock master cylinder. all of this has  led me to believe that trapped air is at the heart of almost all of these systems' sponginess.

[jensk]

Thank you for all the good responses.
I will let my thoughts wander elsewhere next time I talk to this dealer.

Regarding bleeding I obviously haven't found the right angle of the steer and bike for all the air to escape the system. In my many attempts to bleed all air out of the system i mounted the 1 meter tube as described. Then waited till the next day. Pulled the lever many times to get some motion into the system to get the bubles moving. I could se the fluid moving up and down in the tube accordingly. I could also se very tiny bubles escaping the system through the tube but no air comming out of the compensation port in the reservoir. I repeated the procedure the next day. Unfortunately with no better braking as a result.

When using all my force I can pull the lever all the way to the handle and when driving I have very lame brakes. When i write lame it describes the situation where i with the lever pulled all the way you can still rock the bike a centimeter or to when i pushing hard. On top of this the brakes is sticky.

I shall remember to include that I have new EBC black type pads and I can allmost guarantee that they are not contaminated as I was very careful not putting grease or any other lubricant on when mounting them. The disc was wiped with acetone to clean it of lubricants.

The disc is 4mm thicker than the minimum size. I have tried to rub the surface of the disc with 60 sanding paper but the disc surface almost looks like before. The metal in the disc seems very hard and the sanding leaves allmost no traces on the surface. Maybe I should try using my sanding tool (don't know the english word for this kind of appliance - electric vibrating and revolving tool normally used to sand surfaces like wood etc).

Since everything is new except the mc and the lower brakeline is new my next step is to get a braided lower brakeline. I will take the caliber and brake pipe to the other dealer on tuesday to get him to mount a new type of joint in the brakepipe. Then mount a braided lower line and se if this helps.

The situation is a bit frustrating since i have everything else ready for pasing the registrations test to get license plates. I had the last electrics fixed the day before yesterday.

It would be great to have this solved before she's getting 30 which is 3-4 weeks from now - her first registration being may 1977.

[TwoTired]

If you are going to do the overnight gravity bleed, I suggest you close off the bleed nipple.  Any negative pressure inside the caliper can suck air in past the nipple threads. And, if there are bubbles up by the masters bleed hole, the movement of the fluid can simply push them away from the hole rather than out the hole.  You need some pressure in the fluid vessel to force out the air.

The front disk is stainless steel and very hard indeed.  Tooling this material usually requires carbide.  Scuffing the disk is a good idea to rapidly seat new pads.  I believe I used a knife sharpening stone, the last time I scuffed the front rotor.  They are available in different grits.

It is an interesting point about the pad material.  Do you know what the pad composition is?  Some pad compositions trade off friction qualities with embedded heat transfer materials.  Such pads require more pressure to produce friction.  These pads are produced for lots of heavy high speed use so speed fade and heat fade are minimized.  Some don't particularly work well UNTIL they get very hot.  Racing or heavy duty pads may be like this.
I'm not familiar with the pads you've purchased. 
But, the pedal pressure went up noticeably in my truck when I changed the brake material from organic materials to sintered iron.
Was their a reason you didn't use Honda's street use pads?

Cheers,

[paulages]

don't know what material your sandpaper is made of, but alluminum oxide is one of the toughest abrasives known to man, a "9" on the Mohs scale of mineral hardness, diamond being a 10. here in the states, aluminum oxide is quite common, and should scuff stainless steel quite easily.

i've never used EBC pads, always opting for hondas.

[jensk]

Used my hand grinding stone to give the disc a good grind. Grinded it in a radial pattern. Meassured the disc again a 10 different points. It is 7.5 mm and is stamped with min thickness = 6 mm. Conclusion disc ok.

Assembled brake with the old rubber lower brake line to se if the disc grinding had helped a bit on the lameness of the brake. Bled the system through the reservoir as instructed by TT. Tappet light on the caliber with a piece of wood to get the bubles to rise in the brakeline to the reservoir. After 30 minutes i had a fairly firm brake feeling at the lever. The brake wasn't sticking - great maybe i was getting somewhere.

Took her for a short ride to test if lameness was gone. I felt a ok brake effect when i pulled the lever. Couldn't pull it all the way to the handle.  Still I can't brake effect enough to block the front wheel. As i have never used a soch/4 before I do not know if this is enough/as these front brake are?

Unfortunately after the brake test - about 10 times braking maximum on front wheel only from 60 - 80 kph - i had a sticking front brake. Disc was so warm that the raindrops evaporated from the disc the moment they hit it.

I am still a bit puzzled about what makes the brake stick after the test and not before except if it is the repeatedly pulling the lever maximum during the test makes the lower rubber brakeline collapse inside.

I guess that the next step still is to get a braided lower brakeline and a new joint on the brakepipe.

[jensk]

Now the sticky frontbrake is not sticky anymore - great - GREAT.
 
Aparently it was the combination of an old rubber brakeline and that one of the bolts holding the brakeanchor to the frontleg where the thread was wery gone.

I got a helicoil in to fix the thread, mounted the braided brakeline and now eveything works as supposed to. I can even block the front wheel  pulling the level all the way. And the brakepads are retracting well so the wheel is turning freely

Best of all the brake is very firm. I suppose that it is the result of the new braided brakeline.
Thank you to all of you who helped me on tis issue. This is a fantastic forum.
/jens

[Kamal]

IMHO,  I think anyone who rides these bikes should do themselves a favor and purchase a $30 used front master cyl. off a newer sportbike, and put this on your bikes.

I have done this with the dual disc setups I have run on my 750 and 550s, and the brakes feel almost like i am on a new bike.  One finger pressure needed, all the stopping power you can ask for.

Here, again, is the link to article I wrote years ago about this modification:

http://www.mototherapy.net/dualdiscsohc

Good Luck!