Bleeding Front Brakes

[wildcat_lgf]

I've had to take the front brake lines apart when dissembling and re-assembling my ZXR250C and now it I have no pressure in the front brake. (I only detached the LHS front brake line)

I've bleed brakes before (on a cage) and know you are suppose to pump the lever until it gets hard and then open and close the bleed nozzle, but it doesn't seem to want to pump-up any pressure...

How come? Am I just not being patient enough with it? I thought I had...

Cheers

[Paul in NZ]

Yes, some bikes can be a real PIA...

Are you getting any fluid at the caliper?

Some times with old shitters like my Guzzi you need to tie the lever back to the bar overnight (to open the return valve) and loosen the m/c cap to allow any air to come to the top.

However most japanese bikes bleed up OK (well the ones I have tried) so are you sure you have not got an air leak some place or shagged the master cylinder trying to pump it up?

Cheers

Paul N

ps - sometimes you need a pressure bleeder.. It sucks the new fluid through!

[wildcat_lgf]

Yes, some bikes can be a real PIA...

Are you getting any fluid at the caliper?

Some times with old shitters like my Guzzi you need to tie the lever back to the bar overnight (to open the return valve) and loosen the m/c cap to allow any air to come to the top.

However most japanese bikes bleed up OK (well the ones I have tried) so are you sure you have not got an air leak some place or shagged the master cylinder trying to pump it up?

Cheers

Paul N


ps - sometimes you need a pressure bleeder.. It sucks the new fluid through!

Yeah thats the odd thing, I am getting fluid at the calipers...surely the master cylinder wouldn't spit the dummy so quickly? It was working perfectly fine about 2 weeks ago (prior to taking apart)? I've checked all the hoses are tightened properly and there doesn't appear to be any wear on the hoses either? Could be an air leak I suppose...the only odd thing is the little rubber "washers" under the bleed valve have perished. But surely I should be able to pump it hard and then I would feel the pressure dropping? There doesn't appear to be any air coming from around the valve.

[Motu]

Some times with old shitters like my Guzzi you need to tie the lever back to the bar overnight (to open the return valve) and loosen the m/c cap to allow any air to come to the top.

I don't know this old chestnut keeps getting dragged out - tying the lever in will close the compensating or if you like return port,I can't see that pulling the lever in overnight would do sweet FA - it might be better to walk around the bike anticlockwise three times holding a bottle of brake fluid reciting Stairway to Heaven.

[Paul in NZ]

I don't know this old chestnut keeps getting dragged out - tying the lever in will close the compensating or if you like return port,I can't see that pulling the lever in overnight would do sweet FA - it might be better to walk around the bike anticlockwise three times holding a bottle of brake fluid reciting Stairway to Heaven.

That works but only if you recite it backwards..

I have done this on the Guzzi but not all the way back. methinks the bubbles just rose to the top of the hose over night and bubbled into the MC in the morning. I suspect the tying the lever back is just supposed to make you feel good about it? Dunno...

I do know the rear caliper on the Guzzis linked system is a right bastard to bleed and I had to resort to taking it off the bike and tying it up above the MC over night to get the air to it but thats another story..

Cheers

[bugjuice]

just get someone to pump the lever while you're watching the bleed nipple. As soon as the fluid squirts out without spitting, hold the lever in tight and close the bleed valve. Do one caliper at a time, and try to protect the tyre, rims etc from the fluid. Make sure the fluid tank is topped up while doing this too.

An alternative, if you can get hold of an old syringe and some plastic tubing that'll fit neating and snug over the bleed valve, then suck the fluid down into the syringe. When the tube is full of fluid without air (and the tank on the bars is still full), close the valve.

[dickytoo]

sometimes the air bubble gets stuck right at the top of the brake line near the master cylinder. you can try cracking the banjo bolt to release this air bubble when you're bleeding the brakes.

an easier way would be to buy a special banjo bolt from the shop next to motomail for about $20 and use that to help with the bleeding process. this bolt has a bleed nipple built into it. i have used this on all the bikes i've had and it works a treat. you simply replace the old banjo bolt and put the new one in. you have to tell him the size, usually 10 mm and how many brake lines go into the master cylinder at that junction. some bikes have both brake lines going into the master cylinder requiring a longer bolt and others, use a single line into the master cyclinder and some form of junction lower down.

[Motu]

Air wants to rise to the top - there is not enough volume in the master cyl to push all the fluid and air out in one stroke,so the air just stays in the hose.Of course there is always a simple way - invert the motorcycle...this puts the master cyl at the bottom and the caliper at the top,you will find the brakes bleed perfectly using this foolproof method...

[bugjuice]

Air wants to rise to the top - there is not enough volume in the master cyl to push all the fluid and air out in one stroke,so the air just stays in the hose.Of course there is always a simple way - invert the motorcycle...this puts the master cyl at the bottom and the caliper at the top,you will find the brakes bleed perfectly using this foolproof method...

true, so the other way I have done it with the syringe thing, is put the fluid in the syringe, then push it in via the bleed valve. Gotta be the best sure way for no air at all.. fill from the bottom up.. Just might get a bit messy at the top. But the lever keeps it a one-way system, just about, doesn't it?

[sAsLEX]

when Milky mainly did my brakes we ended up with them pretty much devoid of any fluid in them so there was air to affrica, so we found in his garge a power bleeder for old brittish cars , this meant we could force fluid through the system under pressure and remove most of the air that way/

[wildcat_lgf]

Awesome, good to know I'm not the only one having difficulties here

I think the syringe or similar system may work, or if I get a chance I'll get that banjo bolt thingy...

Cheers

[Motu]

If you have a rubber top hose - pull the lever in,clamp the hose,release lever...compress lever,clamp,release...etc.

[John]

Just a stab.

Why not take the callipers off and hold them above the master cylinder while bleeding.. would make it easier would it not?

[Ixion]

What's wrong with the old jar of brake fluid and a tube over the bleed nipple ?

[dickytoo]

Awesome, good to know I'm not the only one having difficulties here

I think the syringe or similar system may work, or if I get a chance I'll get that banjo bolt thingy...

Cheers

I'll try and enclose a couple of pictures of the banjo.. here's hoping!


BTW, you shouldn't pay more than $30 each.