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Discussion Starter #1
Hi,

I have a serious problem with my brakes. I have a 2005 F4 1000S.

Today I went for a short ride after winter hibernation. Meaning that I haven't ridden the bike for almost 6 months.

The bike start up normally and everything felt normal. But then after aprox 3 miles the front brakes started to behave weird. When I used the brakes the brakes would let go after I had stopped breaking. Causing a total lock-up of the front wheel.

The master break cylinder was completely jammed. Meaning the break lever was in the most outward position and I couldn't squeeze them even for a tinny bit.

So there I was in the middle of the road and I couldn't even move my bike. I called my friend to bring me some tools. By the time she got to me (10-15min) the brakes let go a bit (they were still grabbing a little bit) so I at least could drag the bike away from the middle of the road.

Then I wanted to release the pressure inside the brakes by unscrewing the bleeding nipples on the calipers. A few drops of brake fluid came out.

Then I drove the bike without using my brakes back home. Now the bike is in my garage and I don't know what to do?

By now the calipers have completely let go and the wheel is free to move.

I am not an expert when it comes to brakes and mechanical stuff. But in my opinion the master brake cylinder jammed up and after squeezing the lever and it didn't release the pressure in the hoses as it should.

So any thoughts? Advice? Anyone also had problems with their master cylinders ?

Thanks
 

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This is a new one on me...

Have you changed the fluid??

5.1 brake fluids good to use and should ideally be changed each year anyway

Flush the system, replace with new fluid and see how that goes-

While your at it check the prisons in the calipers too, just incase they're binding- its my guess they'll be fine and the issues some damp in the lines / fluid and it's contaminated your fluid which could of got extremely hot under use, expanded and locked the pressure up-

Let us hear the results- ideally you'll see some milky fluid in the lines when flushing then it's problem sorted
 

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James may be on to it as water in the lines will boil under pressure and expand in the lines forcing the pads onto the discs...

But I would service the brakes thoroughly. Check your brake pads for wear. If they are worn down then the pistons may be coming out a long way when you apply the lever. If then you have dirt / corrosion on the exposed areas of the caliper pistons then your brakes may not back off after applying pressure as you would want them too.

So I would take off the calipers, check the brake pad wear, clean the caliper pistons where they are exposed and then massage them in and out using common sense and a bit of plywood or similar to prevent the pistons popping out of their bores.

I would then fit new pads if needed and push the pistons back. I'd then refit the calipers and bleed the system to fill with fresh fluid.

If you still have a problem you need to check the master cylinder for correct operation.

My instincts point to the calipers..or as James says water/contamination in the hydraulic fluid.

I hope you sort it out ,

joe
 

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Discussion Starter #4
Hi James,

thx on the input.

I've changed the Break fluid exactly 1 year ago. I do that each year.

I'm scheduled to do maintenance on my bike this week, so I'll fully investigate what you've just mentioned.

But I didn't noticed any extra heat on the brakes at all. I checked by hand when it happend.

Is there a way the reason for the malfunction is the seal system in the master cylinder? I haven't seen the inside of a one.

I'm afraid that a similar malfunction occurs again. When it comes to brakes I want to be 100% sure.
 

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Discussion Starter #5
Thanks Joe,

I've just bought a new set of brake pads. So I planed to change them anyway.

But the pads are not worn too much. They still have around 40% left in them. And the bike has 18.000 km ...
 

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Water.
He said he had not ridden it for 6mths. B fluid is highly absorbent and some water may have been absorbed into his system during the inactivity.
He said after he rode a little, Lock up happened. The water heated up and expanded.
Then he said after he left it for a while he was able to move the lever a little. The water cooled and condensed again.
The reason I dont believe it is a stuck caliper is because he says it releases after being left alone.
Recommendation, full flush of the system.

That is what I belive and what I would do, but you may wanna check with Knurl, he would problaby have more knowledge on this......... and he's old. Old guys know alot of stuff :) hahahah

Tree
 

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Well ..He needs to fully service his front brake system as whatever is causing it is what it is ...

If the pads were jamming onto the disc then the heat would cause expansion down there and then back off as the disc and pads cool..Who knows..He needs to get the wrenches out and have a look see.

Tree is right on the brake fluid tho and a point to bear in mind with Dot 5.1 is that it has a higher WBP but is also more hygroscopic than Dot 4.0. So therefore James is on the the button with his policy if changing it once a year.

I think the race guys change it out much more frequently !

joe

joe
 

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Have never had it happen on a bike but have had these exact symptoms in cars and pickups when there was air in the system.

Toby
 

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locked?

its the piston in the M/C, something isn't letting it return to the at rest position and opening the return port allowing the pistons to retract.
moisture/water won't do it, but a piece of dirt could in theory block the return port

make sure the brake switch is correctly mounted
check the adjustment of the brake lever adjuster. is it ALL the way out? (for you guys with big hands)
mine will just start to move the piston when adjusted all the way out

people have this trouble all the time with the rears

when playing with the push rod or changing footpegs/levers

Brembo radial front M/Cs have an adjustable pushrod that will cause the problem too:jsm:

flush the system 1st
 

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Discussion Starter #11
I'll flush the system and change the pads. That's sure.

But I'm afraid something is wrong with the master cylinder. Something like the knurl mentioned, like a clog (dirt or something). Is there a way to open the master cylinder and see whats wrong? And by doing so is there anything I can F*** up ?
 

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Just realised who you are lol :) Hi Simon....

Im Not sure about the master cylinder internals mate-

Try new pads & check the pistons at the same time

Flush the old fluid and replace with new 5.1

Take it for a steady test ride and see how it goes-

If it persists then zap us back on here- it may need a new lever / master cylinder but id seriously doubt it

Just talk to yourself and convince yourself you deserve the best and go and get new lines and a shiny pair of Brembo RCS Radial Levers :) :) :) :)
 

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Discussion Starter #13
James, you realize you have just updated my bike's wishlist. :mouthwate

But first I have to wait for my master mechanic to give me the news on what's wrong. And then have a look at my piggy bank, to see whats left inside
 

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Use Dot 4 mate, Dot 5.1 is overkill on the raod and as Joe mentioned, goes off even quicker. Changing pads have nothing to do with your problem, but while your at it take a look at them.
You can remove the M/C and dip it in brakefluid for a short time while pumping it to make sure you get any blockages out. I don't suppose you had a chance to check if it was both calipers sticking ?
My money would be on it being one of the calipers, these Nissin M/C's are pretty reliable in general, not so much the calipers though.
 

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Skonda,

If you need an o/e mastercylinder, I have a new unused one spare. I may also have a used one. Hopefully you can fix this without needing to change your mastercylinder though. Let me know if you need any help.

joe
 

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Discussion Starter #16
@Donsy: When this happened to me I checked both the calipers, and in my opinion both were gripping. But I'm not 100% sure.

The facts are: On Both sides the pads were touching the disc, the pistons were in the outer position, the temperature on both sides was the same. The wheel was blocked. ----> So I assume both calipers were gripping. (But I'm not a expert mechanic)


@Joe: Thank you for your offer. As soon as I discover what caused this problem and if I'll need a new nissin master cylinder I'll contact you.
 

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On cause for this that I did not see, my apologies if I just missed it, is over filling the master cylinder reservoir. This happened to me once and I took each caliper one at a time and with it off the bike pulled the brake lever very slowly. I observed how the pistons moved. One moved more freely than the other. I let come out a little but not enough to fall our and cleaned it thoroughly with a tooth brush and WD40. I then pushed it back in, and then locked it in place with a small C clamp. I blocked the other four and made the opposite one come out some and cleaned it and then blocked off those two and continued this until I had cleaned all six. I cleaned off the mounting pins for the brake pads with some fine steel wool. I also removed the rattle clips so the pads would move freely back away from the rotor.

I now have better feel and the brake no longer locks. Of course I flushed the whole system at this time and made sure it was not over full.

Jim
 

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+10

On cause for this that I did not see, my apologies if I just missed it, is over filling the master cylinder reservoir. This happened to me once and I took each caliper one at a time and with it off the bike pulled the brake lever very slowly. I observed how the pistons moved. One moved more freely than the other. I let come out a little but not enough to fall our and cleaned it thoroughly with a tooth brush and WD40. I then pushed it back in, and then locked it in place with a small C clamp. I blocked the other four and made the opposite one come out some and cleaned it and then blocked off those two and continued this until I had cleaned all six. I cleaned off the mounting pins for the brake pads with some fine steel wool. I also removed the rattle clips so the pads would move freely back away from the rotor.

I now have better feel and the brake no longer locks. Of course I flushed the whole system at this time and made sure it was not over full.

Jim
You are spot on there Jim - overfilling can cause lock-up too.
 

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overfilling?

You are spot on there Jim - overfilling can cause lock-up too.
Donsy;
i don't think so.....with radial Brembo M/C on my Aprilia it takes ~300PSI to get the tire to squeal.....i measured it:naughty:

with the rubber accordion gaskets in M/Cs you won't have any pressure, how can you create pressure as you screw the cover down?
 

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Donsy;
i don't think so.....with radial Brembo M/C on my Aprilia it takes ~300PSI to get the tire to squeal.....i measured it:naughty:

with the rubber accordion gaskets in M/Cs you won't have any pressure, how can you create pressure as you screw the cover down?
1. Ignore protocol
2. Push accordian ALL the way folded up and in...or forget to put in...
3. Make DAHAMN sure your pistons have been pushed to the "out" limit agaisnt the discs
4. Overflow your reservoir spilliing over theedge on a level surfac
5. Plug the vent in the reservoir cap
6. Cram the cap on
 
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