Brakes won’t bleed

[Farmingstock]

The bike had been stood for a while so I decided to change the fluid before MOTing the bike (Rieju 50cc) rear brake

I’ve tried every which way to bleed the brakes and it’s not happening.

There is no fluid in the system, I have tried the following:

Filled the res up tried bleeding but it doesn’t seam to move from the res as the level isn’t going down.

Used a vacuum pump but it doesn’t suck anything through

Tried reverse filling but ended up with fluid everywhere when the pressure blew the pipe off

Tried bleeding for a good few hours with no joy

Taken off the MS seals are fine and build pressure

Taken off the caliper, seals and piston are fine and piston moves as it should

Brake pipe is clear.

Tried to bleed at the banjo instead and nothing

Can’t bleed at the MS banjo due to the design of the bike and no access.

Any other suggestions?

[xX-Alex-Xx]

Vacuum pump should work... You did have the cap off the reservoir when you tried?
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DILLIGAF

[Farmingstock]

Yeah cap off the res, it just doesn’t seem to move any fluid out of the MS res, the vac pump builds up on the pump but when I open the bleed nipple the pressure drops instantly

[Easy-X]

Sounds like a blockage somewhere. If you disconnect the pipe from the master and try a reverse fill it should piss out the end.

My bet is either a rebuild of the M/C required or something stupid like the bleed nipple is totally bunged up.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[jaffa90]

[quote="Easy-X"]Sounds like a blockage somewhere. If you disconnect the pipe from the master and try a reverse fill it should piss out the end.

My bet is either a rebuild of the M/C required or something stupid like the bleed nipple is totally bunged up.

[jeffyjeff]

1. Taken off the MS seals are fine and build pressure
2. Taken off the caliper, seals and piston are fine and piston moves as it should
3. Brake pipe is clear.
4. Tried to bleed at the banjo instead and nothing
5. Can’t bleed at the MS banjo due to the design of the bike and no access.

Assuming MS indicates Master Cylinder.

If you cannot bleed at the master cylinder banjo, how do you know that the seals are fine and build pressure...resistance on the brake pedal?

When you tried to bleed at the banjo (caliper end) you should have made a big fucking mess. If you did not, the problem lies before the caliper. Everything you have written suggests a blockage between the master cylinder and caliper.

First, confirm fluid is flowing through the line to the caliper. Remove the line and direct into a cup, then pump the brake pedal a few times to draw down fluid in the master cylinder.

If fluid does not flow, I would remove the master cylinder and brake line; disassemble, clean, and inspect. Blow out the brake line with compressed air to ensure no restriction. Assemble the system and bleed.

If you confirm fluid is flowing to the caliper, your problem is in the caliper. Most likely a knackered bleed screw.
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History shows again and again how nature points out the folly of men - BOC

[bikenut]

Sounds like the tiny hole in the master cylinder is blocked.

This tiny hole is the recuperating port that allows fluid return from the caliper when brakes are off.

Post a picture of the master cylinder which may have a remote reservoir.

Is a seal kit available ?

If the reservoir is full, the hose clear, the bleed nipple clear and open, fluid should drop out due to gravity/Syphon.

You say you tried back hleebing but the hose blew off.

You could use the caliper to back bleed but fluid needs to be in the system, else the system will not pressurise...

Picture and seals ?

Your probably gunna have to strip the master cylinder.

Do you have a guitar ?
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nuts about bikes

[Nobby the Bastard]

The easiest way to find out if it's the master cyclinder is to undi the banjo at that end and see if you can get brake fluid in by reverse bleeding. You should be able to tell if the fuild is going in quite easily.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[kgm]

I too would suggest stripping the master cylinder. Although realistically you can buy a whole new master cylinder and lever setup off eBay for about 15 quid.

At this point I'd strip and clean everything, new seals all round. Cheap and easy on that bike, could be done in an hour.

[xX-Alex-Xx]

[Farmingstock]

thank you for the responses,

I had completely removed the brake set up to check everything but the MS isn`t accessible once fitted to the bike, meaning everything has to come off again to check anything.

I put fluid in the MS when it was off the bike, finger over the end and pumped a bit of pressure and a dribble of fluid came out it didn`t spray everywhere, just a dribble.

The seal kits and MS its self are not obtainable in the UK and definitely not for £15-20.

I have tried filling from the caliper and fluid comes out of the pipe.

Looking like an issue with the MS, can you buy generic seals and anyway of measuring them?

Cheers

[Bhud]

Can you remove the piston? Try pulling it out completely and pushing it in again a couple of times, in case there's a bit of dirt or something blocking the in or out fluid holes. This might be enough to push out an obstruction. Make sure you don't put in any kind of fluid except brake fluid.

If you're going to replace seals or any brake parts at all, I recommend you stick with OEM.

[Ayrton]

What model bike Reiju is it? You can buy whole master cylinders with the brake calliper for some of these Chinese bikes cheaper than a seal kit may even cost
https://www.ebay.co.uk/itm/173831628710?epid=5030234721&hash=item28792c27a6:g:LMYAAOSw-lVhqDZv

[Nobby the Bastard]

Was it working before you decided to change the fluid?

If so, you've probably dropped something into the master cylinder.

Always assuming you didn't remove the whole system just touching the fluid...
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Farmingstock]

It’s an RS3 2018, I’ll get a picture of the MS when I take it off but it’s not a generic one unfortunately.

The rear brake was very soft and spongy prior to removing the fluid, didn’t stop the bike.

I cleaned everything before refitting, may remove again and put in ultrasonic cleaner just to make sure it’s perfect.

Is there a test to make sure the MS is fine??

[Farmingstock]

Taken the MS off again! I can definitely get fluid back to the banjo at the MS by pumping back from caliper bleed nipple!

[bikenut]

Post a picture of the res floor.

A large hole more towards the phone stone rod and a tiny hole nearer the hose end


They may be covered by a tin "roof".

You did assemble the MC correctly.

You said on initial inspection that there was no fluid in the system and the brakes didn't work, so its leaked out. Good thickness of pad material ?

Any staining on the pedal end of the MC ?

Any staining on the floor of its resting place below the MC ?

With MC assembled correctly and res filled with fluid, fluid should drip out of hose end...

Do es that happen on the bench ?
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nuts about bikes

[Farmingstock]

There was fluid in the system I was just changing it as the rear brake didn’t work properly, didn’t stop the bike but if on a stand it would slow the rear wheel if I turned it by hand!

The MC definitely wasn’t leaking before hand and doesn’t leak now either.

Trying it on the bench it doesn’t seam to build any pressure, it will dribble fluid out when I put my finger over the end but definitely doesn’t squirt out!

The piston has some marks on it like someone has messed with it before.

[bikenut]

Picture fuzzy but seals look the right way.

Still not picture of res floor.

The MC should pump fluid...

Is that tiny hole blocked ?

Shine light into res and look down bore, you should see the light ...
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nuts about bikes

[Farmingstock]

The holes look clear

[Polarbear]

Surely that is a generic master cylinder made by an outside company and available from other sources? I mean, even the big Japanese M/C companies buy in their brake components.
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Triumph Trophy Launch Edition

[Farmingstock]

I’ve looked high and low but nothing!

After an hour of bleeding I am getting somewhere, however each time there are lots of bubbles coming through, I have left zip tied the brake on to try and release some bubbles, will see how it goes.

[Bhud]

[Bhud]

[Farmingstock]

Pretty much there I think, probably still some bubbles in there but the back wheel locks up now and the pedal is solid, much better than it was when I started, that is for sure