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Sleeper
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Discussion Starter #1
Hi all.
I recently bought a 2000 XX low mileage. The bike was sitting in a dry garage for years. No rust, everything works fine except for two minor things.
I noticed that the rear brake was not feeling right. When i press the foot lever, the rear wheel feels stuck for only 3 or 4 seconds then seems to release and works fine untill i pump the rear brake again. Pads are not worned out. Brake pedal operates freely in pivot. Brake flush already done the right way.

I did noticed the the secondary master cylinder is stuck. I disconected it from the pivot and tried to pump it by hand and it didnt move. I even pushed it hard using a wrench but nothing. Opened the rear caliper center bleeder and couldnt move the rod either. Is this normal? Can this be the problem with my rear stuck brake? How do i clean the secondary master cylinder?

Thanks.
 

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Welcome Eduardo. No, it is not normal and yes the 2nd master isn't allowing fluid to flow so the rear caliper will stick and if you ride the bike the rear brakes will get hot. From what I have learned on this forum it is a somewhat common problem and if you search some threads, some members have pics of the problem. The master has a valve in it that gets gunked up and a good cleaning or a possible rebuild will remedy your problem. I personally would go through the entire system for piece of mind; brakes are kinda important. Or another option is delink the brake system. Good luck with your new Bird...it is a helluva ride.
 

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Ditto what exxelent said. Strip the entire system, clean, flush and freshen up the entire brake system. There is no half job with CBS. Do it properly the first time, service every two years and it will be sweet for a very long time. No de-link needed. Unless you really want to de-link.
 

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Sleeper
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Discussion Starter #4
UPDATE:

Last week i did a full brake fluid flush using a professional vacuum bleeder and did it as the manual says. Today i took the secondary master cylinder out and striped it. I was amazed by the quantity of brown "MUD" inside the cylinder. The one way valve was completely blocked due to the plastic mesh grill completely full of this mud. Cleaned everything with brake cleaner and put it back together. Now it works smooth and almost no effort.
Took the calipers appart also. Same story. Full of mud behind the pistons. I`ll post pics later.
Didnt bleed the system with new brake fluid yet, but i believe my stuck rear brake is a thing of the past.
 

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I have the same problem, my cylinder isnt moving either. Additionally i have squeeking sounds from the front when using the rear pedal. Aaaaand i am questioning my wiring; is this correct?

20170105_210928.jpg
So i will also strip the secondary master cylinder and clean it. What is the correct lenght of the pushing rod and how is it measuered?
 

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Front brake system.jpg Rear brake system.jpg

Here is a diagram for the hydraulic system, Front and Rear master cylinder activation. The secondary master cylinder for the rear brake actually controls the two outer pistons on the rear caliper.
 

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Well done for getting stuck in eduardo, that brown mess is a sure sign that the fluid changes have been neglected badly.

Kosmodian, the push rod length is set and shouldn't be altered ..... the factory service manual doesn't even give a length but when you pull the secondary apart you shouldn't need to touch the length. On the squeak, when us Brits started putting braided lines on many years ago about 50% of us started getting 'the squeak' we never got to the bottom of the problem but I've been living with it for 80K miles and even though calipers have been pulled, hoses changed secondary stripped etc the squeak is always there ..... my suggestion is ignore it!
 

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Hm...what if i did alter it already?^^ Can someone measure his push rod lenght (xD) for me?

And what about the one way valve installment direction?
 

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Hm...what if i did alter it already?^^ Can someone measure his push rod lenght (xD) for me?

And what about the one way valve installment direction?
Hmmm, I did the same thing. I'll follow this thread to find out myself because,,,,,,,,,,,the only measurement I could find that related to the SMC was for a Goldwing and although it was different set up, it got me thinking about how it works and what it does. This is what I did but, YOU MUST find out yourself what is correct!!! I made sure the assembly rotated freely and full stroke was obtained (before I filled the system). I adjusted the linkage so that the inlet port was clear and the brake lines weren't being pulled too much by the weight of the caliper, i.e. I didn't want the caliper dropping too far. Just enough to clear the inlet port Hopefully someone will have a non-interfered with linkage and will let us both know what the correct measurement is. Cheers
 

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Sleeper
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Discussion Starter #12
NEED SOME HELP HERE...

For those of you who have taken the one way valve apart...i cant remember if the OWV housing was sealed by one or two o`rings. From the pic i have taken, it seems that there is a thin o`ring marked as red. But i cant find it anywhere. Maybe its just a weird pic effect. The one inside, marked as white is in place.
Do you guys know if it uses one inside and another outside?????

PS- I dont know about the rod lenght...but mine was almost full in. The 10mm bolt was about 1mm far from the 12mm bolt. You can see in the pic.

The plastic one way valve is mounted like in the pic. I can even see the golden tiny ball inside the mesh.

HELP PLEASE.
 

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Can't give a definitive answer to that without pulling a SMC apart (think I have one in my spares boxes) but normal engineering practice says there should only be one seal otherwise from your photo you would have two seals pressing against each other.
If nobody answers overnight I will get into the garage tomorrow ...... and I will measure a push rod as well.
 

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Discussion Starter #15
NEW UPDATE

I can only work on my bike when i leave work, so...

Cleaned secondary master cylinder, cleaned front calipers, cleaned rear caliper...no drag at all in the pistons...put everything together and SAME STORY.
Rear wheel is now dragging more than it should. Front wheel doesnt drag that much. When i press rear brake pedal, rear wheel gets stuck for 2 or 3 seconds, then releases for itself, but the rear wheel keeps dragging.

Only thing i didnt took apart was the rear master cylinder. Dont know if has something to do whit it.

Im full of brake fluid in my hands an shoes...i`m tired.

Help please.
 

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I are the grammar police
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Im full of brake fluid in my hands an shoes...i`m tired.

Help please.
Hey Eduardo,

I'm going to come in from left-field here. :)

When covered with brake fluid, exhausted and p*ssed off... now is not the time to do anything.

Put everything down!

Take a shower, grab a beer/tea/food/loved one (or all of the above) and do anything... anything... but whatever you do... don't try to figure out nasty, ugly brake parts.

There'll be tomorrow. It's Friday night... in Portugal. :)

LOL.
 

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NEW UPDATE

I can only work on my bike when i leave work, so...

Cleaned secondary master cylinder, cleaned front calipers, cleaned rear caliper...no drag at all in the pistons...put everything together and SAME STORY.
Rear wheel is now dragging more than it should. Front wheel doesnt drag that much. When i press rear brake pedal, rear wheel gets stuck for 2 or 3 seconds, then releases for itself, but the rear wheel keeps dragging.

Only thing i didnt took apart was the rear master cylinder. Dont know if has something to do whit it.

Im full of brake fluid in my hands an shoes...i`m tired.

Help please.
Makes sure the head is fresh and clear before playing with CBS! Did you pull the delay valve and proportioning valve apart and blow out all the lines? The crap that developes in poorly service brake systems will clog everything including brake lines (rubber and steel). If any valve or orifice is blocked or restricted, it will hold enough pressure in the system to hold the pistons out. Remember it is only the piston seal which retracts the piston. The seal flexes a very very small amount. It is not a spring, so any degradation in any part of the system will affect any part of the systems performance. Don't forget when playing with the DELAY, PROPORTIONING SMC valves - PARTS MAY NOT BE AVAILABLE. Hope it works out well for you without too much fuss.
 

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Sleeper
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Discussion Starter #19
Ok. thanks for all input guys.
But before i get to mess with the brakes again...for what i understand about the tech draw of the CBS, i can tell that when i operate the brake pedal with the bike standing, there is no oil flowing in the secondary master cylinder...so no oil in the proportional valves either. The problem with my rear brake is only when i press the pedal and the bike is stopped. Rear caliper gets stuck for some seconds. Front wheels spin free.
Last chance would be the rear master cylinder. Brake oil flows well and strong from all brake bleeders, so i am not thinking about any kind of obstruction in the hoses or calipers.
Even without pumping the brakes, rear wheel drags way more than the twin caliper front wheel. Doesnt make sense.

Lesson to be learned: Its better to buy a high milleage bike fully serviced than a low milleage one service neglected.
 

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Eduardo said:
The problem with my rear brake is only when i press the pedal and the bike is stopped. Rear caliper gets stuck for some seconds. Front wheels spin free.
That tells me a lot, since the brake pedal only operates the centre piston.
Try pushing the two outer pistons back into the caliper (so they can have no effect) and then check that the problem is reproduced.
If the problem is still there, remove the cap from the rear reservoir and check again.
To me it sounds like the fluid is only returning slowly when the pedal is released. Does the pedal move freely on its pivot post when the return spring is removed? In the UK climate they can get sticky if not lubricated regularly.
If the pedal is free to move either the centre piston is sticking or there is an obstruction in the line that is preventing the fluid from returning quickly when you release the pressure on the pedal.
I suggest you check these simple things before tearing into the master cylinder.
 
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