motorbike - front disc brake has no pressure?

Chalk

im beginning to think my bad luck will never end
2 rear punctures and now this.

i really hope someone can give think of an easy or cheap way to solve this as i cant possibly afford to leave it in to a shop again before christmas


basically the front brake lost pressure this morning
the window for the fluid container looks full so i think that either the line is blocked or a cable has snapped somewhere.

i dont know what to look for but im prepared to have a mess around with it.

if anyone has any advice , once again it is greatly appreciated

seamus

Sounds like a leak somewhere in the system. It may not be a line breakage necessarily. Have a mate pump the lever, and inspect the line and the caliper for any signs of fluid seeping out. There'll be a bleeder nut on the caliper. Open this and pump the lever. If nothing comes out (air or fluid), then there may be a blockage somewhere.

If you're not sure what you're doing, get thee to a mechanic!

Chalk

ill check that this evening.

the lever itself is gone really soft , if thats the right word.
it used to pull in about an inch or so but now it goes right in to the bar , would that be a sign of anything else?

seamus

Chalk wrote:

ill check that this evening.

the lever itself is gone really soft , if thats the right word.
it used to pull in about an inch or so but now it goes right in to the bar , would that be a sign of anything else?

(I'm assuming you don't know much about hydraulics here, sorry if I offend your intelligence ). Hydraulics systems are based on the fact that the hydraulic fluid is incompressible. When you pull the lever, it forces the fluid down the tube, and being incompressible, the fluid pushes your brake pads together. Air, however is compressible. So if air gets into the system, you pull the lever, the air simply compresses, and the brake pads don't move.

So if the lever comes back to the bar, that means that either air has gotten into the system, or fluid is leaking out of the system when you pull the lever (both usually occur together). The most common cause of this is line breakage (from wear - they say you should replace brake lines every 4 years). Anything though where wear or damage has occured that will allow fluid out and air in will cause it.

Seth Brundle

tis a sign of a fault alright but could be caused by air in the system or by a faulty master cylinder (assuming there is one!)

Chalk

O_O
i have no clue about these things at all
if the level in the little fluid tank hasnt gone down is that a sign that fluid isnt leaking or is that window unrliable?

if the line is damaged and needs replacing what does this cost do get done professionally / how hard is it to do myself?
if its the master cylinder, which i dont even know what that means, what will that cost?

the bike is a virago 125 if that helps.

thanks

Seth Brundle

As Seamus said "If you're not sure what you're doing, get thee to a mechanic!" - if you are not 100% sure of what you are doing then pay someone to do it! Brakes are too important to mess with!

Chalk

i know, i know.

i just cannot afford to get it sorted this side of christmas so i was hoping to get some sort of interim solution.
i did ask how much it would cost to get someone to do it aswell , in case it wasbe cheap and i could get a loan off someone.

Seth Brundle

tell me about it! me motor has a broken cat (~€1000), needs two rear tyres (~€400) and tax [+arrears] (~€1200). I think Christmas will be spent out begging!

Interim solutions:- www.luas.ie, www.dublinbus.ie, www.irishrail.ie...

Chalk

ok thanks.....

seamus

kbannon wrote:

Interim solutions:- www.luas.ie, www.dublinbus.ie, www.irishrail.ie...

Lol.

Chalk, replacing the lines or the master cylinder is best left in the hands of professionals. It shouldn't be too bad, if you manage to diagnose the problem yourself. If you drop your bike in then and tell them what to do, it'll be cheaper. If you just drop it in and say, "Brakes don't work. Dunno why", they'll lump you with extra labour for diagnosing the problem.

It's not that expensive. At most €200 including new pads and labour.

Canis Lupus

but bleeding a brake system isnt that difficult.... someone point him in the right direction of the bleed valve.... It's worth seeing if it works.

And if it doesn't sure just carry a metal pole... and whenever u want to brake the front wheel just shove the pole in the spokes...and... errr... brace yourself...

Fabritzo

Brake fluid is not very good for the skin as far as I know, wear gloves or something if you're going to feck around with it.

Interceptor

Sound advice, up to the metal-bar-through-the-spokes bit!! Get thee to a Haynes manual - any of them will do so long as its for a bike with a front single disc brake.

Inspect the brake line by following it from the handlebar to the disc - any sign of fraying or seepage means new brake line.

Inspect the disc for oil contamination and clean it with isopropyl alcohol or methylatd spirits (chemist shop) if you suspect that oil or fluid leaked on it when the rear punctures were being fixed. The disc must not be dished, cracked or scored - but this won't affect brake operation.

You should be able to inspect the brake pad by looking at where it rubs off the disc - there should be 3mm of brake material and a metal backing plate at a minimum, otherwise you need to buy pads.

Get a metre of 6mm o/d nylon hose from an auto factor - tell them its to bleed brakes. Get a bottle of fresh DOT4 brake fluid - 250ml should do it, get an empty jamjar and whatever spanner fits the bleed nipple. The bleed nipple is mounted on the brake caliper (the bit which bites the disc), loosen it slightly and push the hose over the end of it - put the other end of the hose in the jamjar. Open the lid off the master cylinder (the bit on the handlebar) and top the level up to the max. Now pull the lever several times and as you do watch for bubbles in the hose and keep the level in the master topped up. When the bubbles stop, pump the lever three times and keep it pulled against the bar - retighten the bleed nipple taking care not to allow air back in (ie don't dawdle). Clean up any excess fluid, top up the master and seal it. Check brake power and if you are happy raise the front wheel by rocking the bike on its stand and check the wheel rotates freely. Ensure the brake power doesn't fade before taking a gentle spin.

My guess is the pads are worn down and aren't retracting, causing the caliper to overheat and the fluid to boil out - caliper rebuilding needs to be left to an experienced mechanic so plan for this possibility. This is the longest post I've typed in some time, I have to go and lie down....

'c

Interceptor

Fabritzo wrote:

Brake fluid is not very good for the skin as far as I know, wear gloves or something if you're going to feck around with it.

Occasional contact with it won't do any harm - it eats paintwork and can cause dermatitis. Don't drink it and don't rub it in your eyes. Used engine oil will give you cancer if you just stand near it though.....

'c

Elfish

interceptor wrote:

Get a metre of 6mm o/d nylon hose from an auto factor - tell them its to bleed brakes. Get a bottle of fresh DOT4 brake fluid - 250ml should do it, get an empty jamjar and whatever spanner fits the bleed nipple. The bleed nipple is mounted on the brake caliper (the bit which bites the disc), loosen it slightly and push the hose over the end of it - put the other end of the hose in the jamjar.

You have to put a little fluid in the jamjar to begin with - to cover the bottom of your drain pipe and keep system airtight... so keep the end of your drain pipe submerged ALL the time or you're wasting your time. This is why you will need a pal to give you a hand to do the job properly - 1 person to do bleeding another to pump lever and keep master topped up.

interceptor wrote:

Open the lid off the master cylinder (the bit on the handlebar) and top the level up to the max. Now pull the lever several times and as you do watch for bubbles in the hose and keep the level in the master topped up. When the bubbles stop, pump the lever three times and keep it pulled against the bar - retighten the bleed nipple taking care not to allow air back in (ie don't dawdle). Clean up any excess fluid, top up the master and seal it.
'c

Rather than keeping lever pulled against bar, you will probably have to tighten the bleeder nut and *only then* pump the lever....if you don't tighten up bleeder in between times then you will just be forcing(wasting) fluid through the drain pipe without getting rid of any of the air bubbles. This is trickier than you'd think. Even Haynes manuals don't explain these subtleties too well but you will see what I mean when you do it yourself.So tighten, pump, and then loosen off bleeder again to let built up air out. I have never gotten away with one cycle of this, but then I've never done it on a 125 which has only a single one pot caliper on the front ... so maybe you will get away with one cycle. Only one way to find out.

To reiterate what interceptor has said - keep the level in the filler (on your handlebar) topped up ALL the time. It doesn't have to be right up to the top but it does have to be well above the bottom. You might find this easier if you take out the rubber sealer that sits in it, its easier to see the 'real' level this way and when you're finished just pop it back in.

And don't bait it straight after doing your brakes. You will find that they will nearly always pass intercepters 'roll the wheel by hand' check but it is safer to take the bike gently up and down the road and to check them under real conditions. Even dog poor brakes will pass the 'roll the wheel by hand' check.

Don't be afraid to do the work yourself. Its a cinch once you get the knack and it's easier in the long run than dropping it into a shop.

When you're getting your hose, make sure it's see thru. As interceptor says tell them its for bleeding your brakes. Mountjoy sell the spot on pipe and are best in town for most of the stuff you need. Friendly and helpful too (unlike the cnuts in some warehouse places on the Naas Rd who shall remain nameless!!)

Elfish

interceptor wrote:

Get a metre of 6mm o/d nylon hose

One other thing - don't use a metre of pipe :rolleyes: . Just enough to reach from bleeder to your jamjar on the ground. A foot and a half should be plenty. You don't want to have to fill a metre of pipe full of fluid before your system is airtight...shorter the better.

Elfish

Chalk wrote:

basically the front brake lost pressure this morning
the window for the fluid container looks full so i think that either the line is blocked or a cable has snapped somewhere.

I've never seen a blocked line. Are you sure that the fluid container you are looking at is for the brakes? Are you sure your front brake *isn't* a drum brake? i.e. with a cable ?? If it's a disc brake then you won't have a cable...but if you lost pressure as quickly as you say, and your lever is floppy then maybe you did snap brake cable. I dunno, I had a few 100cc bikes and not a one had disc brake - all were cable. Any one else know what brake a Virago 125 has? Come to think of it you're probably right fella, fluid container *is* for your brake as specs are going up and up on bikes (I've seen some mopeds with snazzy ass disc brakes even !). Therefore you couldn''t have snapped a cable....

seamus

Elfish wrote:

I dunno, I had a few 100cc bikes and not a one had disc brake - all were cable. Any one else know what brake a Virago 125 has? Come to think of it you're probably right fella, fluid container *is* for your brake as specs are going up and up on bikes (I've seen some mopeds with snazzy ass disc brakes even !). Therefore you couldn''t have snapped a cable....

Pretty much all 125s have a front disc at least now. I know the Virago does.

Interceptor

seamus wrote:

Pretty much all 125s have a front disc at least now. I know the Virago does.

Its hydraulic alright.

Pics in ad in for sale Motors

'c

Chalk

well couldnt access boards for ages .....

i went to a bike shop in the end, just to price the work / get a better opinion
said some things from the thread to sound like i had half a clue
...
guy bled the front brake for a fiver and fixed it

thanks for the advise
//
i would have a haynes manual already, was one of the first things i looked for, but i couldnt find one for the 125, they seemed to start at the 535 and thats a completely differrent bike