Horizons Unlimited - The HUBB - Problems with bleeding front brake

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Problems with bleeding front brake

The pistons might have been pushed back in so far that there isn't any room for fluid to get in, you might be able to use compressed air to blow the pistons out a bit and fill the caliper through the bleed nipple hole.
OR you could try back bleeding with another bike and a hose connecting the bleed nipples pump the other bikes brake and open the bleed nipples and siphon the fluid out of your bikes master cylinder.
This can work well to remove bubbles as they are being forced up not down.

Overhauled the caliper and changed the piston in the handle/main cylinder, i have altso bought new brakelines from hel.

I tryed to bleed the brakes for over an hour today, but the oil wouldnt go in. only a small amount. filled up the revisor, pumped the brake many times. opened the bleed valve and did the same over again.

Hiya, well done on the replacement of the valve, if it's in correct, overnight no oil should pass into the brake line or the calliper. Your discription of bleeding the brakes of air appears to be not quite right. Are you opening (just a little to allow oil to pass) the bleed valve as you depress the brake lever, then, closing the bleed valve before releasing the brake lever? To do it this way one should push the air out through the bleed valve untill oil is comming out without any air bubbles in the oil.

noe i have taped the handle to the bar for the night. maby some oil finds its way down the brakeline during the night.

Sometimes leaving overnight is not such a bad idea, as, if there should be any remaining air in the brake line this might* rise overnight to the top and the brake piston. To see if this has happened, hold the lever in, and you might see bubbles of air riseing into the brake resevoir. Having said this, I should add the first operation ought to have done the job of removing all the air in the first place.
* might ! but not likely!

any pointers on what to do

This job is best done with two people.

Have you a bleed valve and line attached to the bleed valve (nipple) or a bleed line that is in oil at the other end?

Hope my comments are of help and makes sense, as its late!

Good luck

Socks

Hi,

also, please be aware that depending on the type of reservoir, low pressure can develop in the reservoir, causing difficulty.
If there is a flexible rubber seal under the lid, leave it off during the bleeding process. I had this problem on a 1998 Suzuki VS 1400. Stuck in New Delhi, it took a sleepless night to figure out what was happening.

Regards,
Mark.

thanks for the pointers. as i walked by the bike this morning i couldnt see a increase of fluid in the revisor.

earlier i have pumped the brakes repeatedly, then held it in while opening the valve on the caliper. if i understand you right i should have the valve open as i press the brakes and close it when its all pressed in?

i didnt know that i could press the pistons too long into the caliper. i guess that i see 1 mm of the piston... but whit the small amounts of brakefluids that i managed to press down the line yesterday i dont think the fluids have reatched the caliper yet.

I rebuilt my caliper and master cylinder on my Dominator recently and installed new Hel braided lines at the same time.
When I went to bleed the caliper the little air trapped in the front caliper stopped the bleeding process, If you want to try filling the caliper you may need to open the bleed screw and fill the reservoir with fluid to see of gravity will take it down.
If the caliper doesn't fill then it could be airlocked, this is where you need to put a piece of wood in the caliper to stop the pistons shooting across the shed and blow the pistons out with the compressed air gun into the bleed nipple port(remove the nipple)
They should come out and you can fill the caliper carefully through that hole.

To bleed the brakes you should remove the reservoir cover.
fill to the indicated level and start pumping with the bleed nipple closed and your ring spanner over the bleed nipple.
You also need a short length of hose from the bleed nipple into a jar or other container with a little brake fluid in the bottom.
This stops the hose sucking air back in as the fluid comes out.

Pump the lever until you feel some resistance, then holding the lever in open the bleed nipple until fluid and bubbles come out the hose.
Keep the lever pulled in, and tighten the nipple again.
Pump and repeat until there are no more bubbles and the lever feels hard.
If you can't get a hard lever, you may have trapped air bubbles, this is where you leave the lever pulled in overnight.
Try and ensure the reservoir is the highest point so the bubbles will rise to it, not some loop in the brake hose.

You could also try reverse bleeding or do what I did years ago and bought a MITYVAC for about £35.

Good bye brake problems...

Some things to check.
Remove the bleed nipple on the caliper and check that the hole is clear (in the nipple).
In the master cylinder, did you fit the piston seal the correct way round?

Also if you are 'pumping' the lever with the diaphram off, cover any paint or plastics !
When I have had similar problems in the workshop, I sometimes use a large syringe to 'draw' the brake fluid through.

Eddie.

Just done my Laverda which has a slightly problematic line layout (a splitter on the yoke). Couldn't get the new stainless lines to fill until I tried this: I got a small plastic bottle with a nozzle on (a small washing up bottle or similar) and squashed it down before connecting it to the bleed nipple with some silicone hose. I then opened the nipple and pumped the lever slowly- the bottle trying to regain its original shape caused a vacuum which really helped move the fluid. Cheap and simples!

if you use compressed air as mentioned put some wood or similar on pistons and be VERY gentle - it only needs a slight 'puff' of air to move them.

you can also just suck on the bleed hose coming off the bleed nipple initially to create an underpressure as you are pumping the brake lever - this works to pull the fluid through, then insert it into a container of fluid and bleed as normal.

but the only drawback is as you suck on the hose you get water vapour bulidup in the low pressure hose which may or may not go through the bleed nipple and into the caliper,even if it did, im pretty sure it would get washed out by the fluid anyway - so any fluid coming out shouldnt be reused.

It can still take a while to get fluid through so persevere

After you're able to get it working, make sure your front disc brake rotor is true!

My front one is bent.. don't ask me how because I got no idea....and when it rotates, it pushes the pistons one way and when you go press the brake it just won't grab the disc as the pistons are to far away...

Vando beer

You need a vacuum. I used a large syringe and a suitable bit of rubber hose to draw fluid from the bleed nipple. All done in about 30 seconds after having the exact same problem after fitting Hel hoses too. Once bled properly and the new pads were bedded in the braking was much more positive.

Regards - Alastair.

it was the pistons on the caliper that was too far in. i need to get a place with compressed air to fix it.

i altso found out that one of the gaskets on my fork is blown. it was dripping oil down on the caliper:( i just changed the fork oil...

where is the easiest place to buy new ones? is it a easy job?

well, If you just changed the fork oil you might be able to drain it back to a clean container of some sort...

I never replaced the seals on my XT forks but have fully dissassembled the YZ forks that I have on my XT and can tell you that it's quite an easy job if you have the right tools..

For a matter of fact, the XT fork seals should be much easier than the inverted forks of the YZ since the XT ones you can take them from the top of the fork whilst on the YZ you have to fully separate the upper and lower forks...

These guys on here should be able to tell you how to do it properly!

Good luck!
Vando beer

I made a guide to disasseble the forks to swap oil/springs after doing it on my xt600e. You just need to take it a bit fuher apart.....Read on :)

Its not that hard, but a bit time consuming the first time, and tricky without proper tools.

You need to take the fork legs apart as i recall, and you need either an airtool or buy/make a special tool.

This is a guide for replacing the springs, you just need to do the same, and then also remove the unbracobolt in the bottom on the fork (loosen it with airtool before you take the forks apart. Or take them apart and weld a size 32 nut (again, as i recall) to a rod, and put it down the frokleg ho hold "against" the unbraco.

-Put the bike on a stand.
-Remove the speedocable fromt he front wheel.
-Remome the brake by unscrewing to bolts. Twist the caliber back and forward, and remove it by sliding it backwards.
-Loosen the 4 nuts on the lover part of the right leg. After that you can take out youre front axle, do that.

-Loosen the tops of the legs, just loosen them 1/4 of a turn so they will be easier to get of in a few steps, youll probably need to remove you're handlebars. Its 4 bolts, and is real easy.
-Loosen the upper mounts for both the legs, 2 bolts and 2 nuts on each side.
-Now do the same for the lower ones.
-Slide the legs down, they are now off the bike.
- Take the top covers of, remmeber you loosend them before, now theyre easy. If you can, put some weight on them to save the threads a bit.

-When you get them of, you will se the spacer, then a washer, and then the spring. Remove that, and set the leg upside down in a bucket. Pump the leg up and down to get all the oil out, and let it drip of.

Heres where you ned to disasseble more, like mentioned at first

-You're now halfway done, i usualle poor one cup of oil down the legs again, oump the leg up and down a bit, and then turn it upside down, and pump it again,. and let i drip of. Thats just to get all the dirt out.

-Now, compress the leg, and poor oil in it to 16-14cm from the top, depending on how hard you want it. You need 550ish ml to do that.
Just use some 10W fork oil for the job.
-Now its all backwards, remeber to put the new springs in correctly. The end which is tightest together should face up.
It kinda sounds like much, but it isnt. You're jsut remomving the front wheel, taking the legs of, and take the springs out, and change the oil.

Hope you can use it.