Topic: Cb550 front disc brake

[CBGhia]

Thanks for that Scottly.... I did that last night but thought I’d give it another go this morning... Started losing the will to live after bubbles still 20 mins later. Did it nice and slowly with the cap off so as not to cover myself but when I put the cap on and did it more rigorously, I opened it to what I can only describe as fizzy pop!!

Did you bleed the system too?

Yeah, it sounds like you need to start at the caliper again.  Bleed it out as much as possible.  Check for any leaks at the junction that houses the brake switch. 
Then after that is all bled through, go back to do the top of the master again.

[Anthub]

You’ll have to forgive me as I’m new to this game, so I’m only going off what’s on YouTube but I’ve bled the brake through the caliper until the fluid was bubble free.. but when the lever was still spongy and when rocking the bike forwards and seeing that the front wheel still moved I checked the master cylinder reservoir and saw tiny bubbles coming from the right hand hole almost every time I applied the brake lever


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[Stev-o]

Continue to bleed the system...

[Anthub]

Okay... cheers


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[Anthub]

So..... I’ve rebuilt the master cylinder.... Bled, bled and re bled the system with the caliper positioned in front of the fork.. checked for any leaks... tied the lever back overnight (still getting the odd bubble in the reservoir when I pull the lever in, but not as bad as before the MC rebuild) ... then I try to move the bike forwards by sitting on it with the lever fully pulled in so that it is nearly touching the grip and pushing it forwards and the wheel front wheel still turns!!!
Any more suggestions folks?


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[DaveBarbier]

Post pictures of your setup. Closeups, overalls, with good lighting. You said the PO had the forks swapped and caliper repositioned, normally only the left fork is machined to properly align the caliper to the disc. When many people, including me, go dual disc with reversed forks you need to either machine or shim the caliper so it hits the disc squarely. Perhaps your forks were altered in a way that makes the pad touch the disc off kilter.


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[Anthub]

Cheers Dave..... I bought the bike a couple of months ago and I’m starting to discover a few issues that were obviously not a concern to the previous keeper... Here’s some photos.. Let me know if you need me to take any more


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[Anthub]

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[RAFster122s]

When you had the caliper apartdid you pull the piston and seal for the piston and clean the square slot for the caliper slot so any build up of crud under the seal is gone and that slot in the caliper body was clean?
Use of red rubber grease for brakes or brake caliper assembly lube on the caliper seal for reassembly. The metal edges of the pad and back of the pad get a light coating of Dow's High Vacuum Grease (or High Vacuum Petcock grease is another way I have heard it reffered to).  This grease will not "melt" and become more fluid when subjected to any temp the caliper will see in operation and it will not migrate or move to other parts it is not in contact with or reach the pad material and contaminate the pads rendering them ineffective.
If you are not getting clamping force by the caliper you have air in your lines or a blockage somewhere.

Or, something is not sealing properly at the brake master cylinder.  If you pull back the master cylinder boot where the line attaches is there any sign of fluid when wiping the end of the MC and the hose up near the end of the MC and where the line bolts on with the banjo bolt?  Doing the same at the piston and brake lever end should not see signs of any fluid. Even when you pull the brake lever and wipe down where the piston is actuated by the brake lever, no sign of any brake fluid or liquid should be found.

[Anthub]

Thanks for the advice Raf122s ....  Yeah, I checked the piston seal and everything is clean... I’ve replaced the master cylinder piston assembly with a rebuild kit and there is no leakage at the banjo end or at the lever. I just keep on getting the odd tiny or two bubble in the reservoir most times I pull the lever even though I bled the system so that it was bubble free at the caliper end. I can literally (with some force admittedly) pull the lever fully to the bar grip and can still rock the bike forwards somewhat. I’ve checked all the joints for leaks and there’s nothing. I’m wondering if the pads are contaminated with something? Still can’t understand where the bubbles are coming from


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[RAFster122s]

Do you have access to a sander that could sand your pads level and cut them back.

BTW, the EBC now make a V suffixed version and it is a higher "bite" pad that will theoretically be superior to the stock normal organic pad.  Get that pad if replacing.  It should really work better as I am not aware of other bikes with these same calipers which do not have a stainless steel rotor.

I think you might get a tiny bit of movement forward but it is going to be the supsension changing the angle to cause this as the forks compress.  You are not going to see an inch of travel for example.  With your calipers mounted with bleeder not at a high point you could still have a bit of air that has collected in the caliper.  Unlikely to be detectable when bleedingthem now, but I would give them an good two-three inches of fluild in your bleeder hose to ensure they are clear AFTER you unbolt them to make the bleeder the high point. T (Take care to not allow the caliper to invert.  A wire coat hanger secured to the top of the tire hooked into one of the caliper bolt holes can help you do this.  A rag between the wire and your rim will protect against any scratches on your rim. If your fender is painted, then tape the edges and top, or          better yet  since you are working      with brake fluid is to tape the edges and top, or tape a rag to protect the paint or chrome and then plastic bag over that in case you have a spurt of fluid.
I always found that helpful.  A bucket of soapy water is a lifesaver for painted surfaces and brake fluid as quick action can prevent damage by the fluid to your painted parts.
Just makes it mess when in a garage is a pain to cleanup.

If the pads are contaminated, it will depend upon what has contaminated them if sanding them back 1/16" or 1/32" or a mm is going to make a difference.  The bike should be able to stop from moving at a stand still pretty easily with stock brakes and pads.

Being able to bring the lever to the handlebar sounds like you have air in the line.  If the wheel will rotate with you off the bike straddling the front wheel holding the bike upright at arm's length and you compress the lever to the grip or vlose to it you should not be able to make the bike move forward unless you are dragging the front wheel to do it.  The wheel will move a bitbut the tire will not rotate and return to its starting  position when that force is removed. A chalked line across the tire and it just visible past the edge of your fender when in a position on the bike that you can return to from pushing or trying to move the bike when on it.

Air in the lines can be difficult to get out of the system sometimes, especially with a rebuilt MC. The MC needs to be bench bled before reconnecting, or bled on the bike before attaching to the brake hose. This way you know you are not introducing air into the brake system. 
 
Often you need to leave the lever tied back on the grip for several days in a row to get the system fully bled.
It does not take a big bubble to make a squishy lever and end up against the grip.  Since you are having to squeeze very hard to get the lever to the grip I am betting it still has air in the system.  It can take several days for the tiny bubbles suspended in the solution to collect at a high point in the brake system  or with other bubbles and form a larger bubble.

It might need a new MC but, let's be sure the system is fully bled first.
You do not have the stock rubber boot that goes over the end of the MC and the brake hose. It is optional if you do not like the look with it.

[RAFster122s]

It might be easier to replace than try to sand them back.  It also could be done with a sanding drum on a drill press with a fence attached to the drill press table and a drill press vice detached to sllide across the table it make a cut on the pads.  The fence would prevent the drill press vice from deflecting away and would ensure the pads were flat. You pull or push the drillpress vice into and past the sanding drum, letting the drum remove pad material with each pass across the face.  The pad would be clamped in the vice so it would remain square-to/parallel-to the drum face.  A course sanding drum works best.

Some things like oil and grease would contaminate the pads and sanding drum when it is used.  The heat would drive any oil from the grease further into the pad as it is exposed.  So, if the pads were grease contaminated they are done.  That is why the Dow Hi-Vac petcock grease is used.  It won't move from the metal surfaces you apply it to.

David

[RAFster122s]

Grease contamination ruins a pad and I have never heard of a means of recovering them by sanding or cutting them back.  You would need to change the sanding drum several times to lessen any contamination from the sanding sleeve.

[Anthub]

Thanks for that really informative update David.... I am going to get a new set of pads (thanks for the recommendation re the EBC ones). The bubbles seem to have lessened in number over the last couple of days so hopefully it’s just a case of being patient and letting them work their way through (the bubbles are the sort of size that you would see rising from the bottom of a glass of beer.. really tiny, and only 1 of them after about 5-10 squeezes of the lever)
I bled the system whilst the caliper was supported in an upright position on the rotor in front of the fork, putting nearly a litre of fluid through to ensure there were no rogue bubbles.
I’m still able to push the bike forwards with the lever fully applied, with the tyre clearly rotating about an inch each time I rock the bike forwards.
I’m also wondering if the lever is right for the bike.
The previous owner has ‘modified’ the levers so that the bobble on the end is removed and when I first took the lever off, two thin washers, the size of the face of the MC piston fell out so I’m assuming these were used to give more leverage (I’ve checked it against images of the stock ones and it appears that the pivot end is the same!!)




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[strynboen]

..try to find a diragram over the internal parts..and thek you have all in the right place..i think you have mounted somthing vrong in the marster..turned a seal the vrong vay..

some marsters have a steel chim as return valve..it sits behind the rubber seal(behind the spring)and Lock for fluid go back..if your"s not are a orginal Honda..it can have this type.(.think to have seem them on Honda too..?)

even if your brake pads is oiled it still must be abel to stopp the hveel..so dont bay new pads, before thek the other Things,,i have alvays vashed mine in fuel..and then burned them dry..use a small gasburner..but its your Money..and ebc/sbs is a danish kompany" Scandinavia brake(erlyer Svendborg braks) systems"so please use some Money..on that.(and make denmark stronger)..even you are british

and only lube the internal brake parts vith a dot 1-5 kompentabel lube..like the ATE..it can vork vith the brake fluid..and do no harm on internal rubber parts..if it ends up in the fluid

[Anthub]

Thanks for that ... I replaced the parts in the MC correct way and it is an original Cylinder.. I take on board what you have said about the pads, I’m just trying to eliminate potential causes but if you say even contaminated pads should grip enough to stop the bike moving then I don’t know what else to do.


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[strynboen]

you can end  to have to thange the pads..
..but try to fix the hydralik problems first.
.you still pump air in the system..it first get get stone hard..vhem all air is aut..(but small bubbels can still kome in the tiny hole).(.even all funktions vell)..the" hard handel" is the only real vay to thek the system..so dont fight some very small bubbels..

normaly the caliber is not the problem..but have seen some put the piston backverd inn ,or damage the seal..by press the piston dry inn..so it cut the seal..
montage of the piston are done by hand...its need only  a light push to go inn..nothing more..if you have a hard job get it in..somthing is prob vrong there too

[Anthub]

Right...  the piston goes in by hand but it does take some effort to be fair.... It pushes out no problem when pulling on the lever


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[strynboen]

yes the rubber seal press against the side..so if you can press it inn vith 2 fingers..vitaut sqvezze some bones or hurt youself..its fine