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redfish 22 Mar 2008 03:01

front brake calipers
 
yamaha yzf600 rebuilt front calipers and reinstalled with new pads..........can't seem to bleed air from system............have let gravity fill...........but still no pressure to bleed..........please help.

Yobbo 22 Mar 2008 06:17

Suck it out.
Seriously...Try to use a clear hose so you can see where the fluid is,suck it till it starts getting near the end and if you've got a spare person,get them to start pulling the lever.
I have done this a few times and it hasn't done me any harm :wacko:

Flyingdoctor 22 Mar 2008 10:43

I haven't tried this but people have had success with tying a cable tie around the front brake lever to hold it on and leaving it for a day. Wrap some cardboard around the grip first to stop the cable tie digging in to the rubber. I imagine it forces the fluid into all the nooks and crannies inside the caliper and gets rid of the air which travels back to the highest point, the master cylinder. This only works once you get some pressure at the lever. If you've got non you can buy kits with a pump to force it in. Google brake bleed kit.

DougieB 22 Mar 2008 17:42

check the method you're using is correct. if there is zero resistance in the lever, then have you rebuilt the calipers correctly and used new piston seals? are the seals between the caliper halves correctly installed? If in doubt, just split the caliper (I assume they are of the spilt-able type) and clean everything up.

for the bleeding, are you closing the bleed valve when releasing the brake lever? a few pumps on the lever, open bleed valve, close bleed valve, release lever, repeat. Is the hose connected to the bleed valve in liquid (brake fluid) so as to prevent air being sucked back into the caliper end of the brake system?

when you've tried bleeding the system, does the fluid in the reservoir disappear? If so, then just keep topping it up, and keep going. eventually the system will fill up and fluid will start coming out at the caliper end bleed valve.

Mark 23 Mar 2008 16:52

Try a syringe
 
HI Redfish,

In the past I've had to use a syringe connected to the brake caliper bleed nipple by a length of clear tube and sucked the brake fluid down from the mastyer cylinder by pulling the plunger back with the nipple open a quarter of a turn. I then close the nipple, seperate the syringe and pipe, pust the syringe plunger back in, reattach the pipe and repeat. You need to keep an eye on the fluid level in the master cylinder and not let it get too low.

I've heard of people filling the syringe with brake fluid and pushing it into the brake caliper, but I have never tried this as I am nervious of fluid spilling out of the master cylinder and damaging paintwork etc.

Brake fluid is very corrosive stuff, I certainly wouldnt consider sucking it through by mouth and hoping my reflexis were quick enough to stop me getting a mouthful of it!

Good luck

Mark

mattcbf600 23 Mar 2008 18:08

The old tried and tested method of manual bleeding (pressured way is much faster but you really need to know what you're doing) is to open the nipple and squeeze the brake lever then close the nipple before releasing the brake - repeat - alot - slowley

You'll think you've got pressure about three times before it actually builds properly and I tend to go through a whole can of DOT4 before I achieve a clean system.

This page is quite handy and is the method I use

HEL Brake Lines - Brake Doctor

m

kbikey 24 Mar 2008 00:34

Get the air out
 
I use a syringe and clear hose method differently than these other folks. I take a plastic syringe and form a lip on the tip by heating a piece of metal hot enough to melt the plastic.Just barley though, you don't want to go to far up. When you have your little edge slip a piece of tubing over it and secure with a small tie wrap.I use battery vent tube for a tight fit,to help stretch it over the nipple put it over some needle nose pliers and spread them.
Put the other end on the brake bleeder nipple and secure with a tie wrap. Hang the syringe upright with a piece of wire. Fill the syringe with brake fluid. loosen bleeder nipple, insert plunger into syringe and push fluid into the caliper.
This always works for me. It is a lot easier to get the air to go up the hose than down to the caliper. Have the resiviour open and keep an eye on the level. You may have to suck some fluid out to keep it from running over.
I have another syringe to pull the excess out of the resiviour. In a pinch you could soak it up with paper towels.
Good luck, K.B.


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