Topic: Brakes will not bleed...read the FAQ's and still nothing

[going4speed]

So I added a new master cylinder from a 1990 CB900 I believe with new brake lines, new banjo bolts, rebuilt caliper, phenolic brake piston, new oring, ferodo pads.

So I get the system as bled as I can following the FAQ and others on this website from extensive searches.

What's going on is the caliper drops to nothing after I close the bleed screw and then it will pump up from there but will remain spongy.

I have tried the 20 fast pump thing the bleeding with a 20mm gap between lever and bar thing, today I installed a speed bleeder, I have tried a vacuum pump.

No matter what I try I get the same drop to nothing and then pump up pressure and the brake holds but is spongy.

Anyone have something else I can try that may work?

[domer]

do you have any loops in the brake line, i had to pull my master off my clubmans to get it to bleed with the stock brake line... sucker goes all sorts of different directions.

[going4speed]

No loops just goes straight down as I put drag bars on and ordered shorter brake lines.

do you have any loops in the brake line, i had to pull my master off my clubmans to get it to bleed with the stock brake line... sucker goes all sorts of different directions.

[the technological J]

you might wanna rebuild the master cylinder

[Kevin400F]

You do have the open end of the phenolic piston against the brake pad, correct?

Kevin

[going4speed]

Sure do. 

Is there a number on the master cylinder somewhere that would tell what rebuild kit I may need?

You do have the open end of the phenolic piston against the brake pad, correct?

Kevin

[the technological J]

here check this out i cant find a 90 900 on here but this might help
http://www.babbittsonline.com/pages/parts/viewbybrand/7/Honda.aspx

[Hush]

On the older bikes one trick I got from someone on here is to attach a clear tube to the bleed nipple and run it up past the reservoir, open the bleed nipple a few turns and leave it over night to let the tiny micro bubbles rise to the surface.
Worked for my 650.

[metalmechanix3]

Is your bike a 90 900? If master is going on different bike is the master piston bore same size as stock for your bike? Also if the bleeder is on the bottom of caliper it can trap air. But does sound like you might have pressure issue with master.

[Rich361]

I had the same problem with my Harley, Bleed the brakes and could not get hard grip.

Saw a tip on the internet, Cable tie your brake lever to your grip and leave your brakes fully on over night...  all the tiny bubbles rise slowly rise and in the morning... nice firm brake!!

Just make sure your reservoir is full...

I did this for a couple of nights... work very well...

Guess similar to Hush's suggestion, but just in reverse...

Cheers

Rich

[going4speed]

Thanks for all the tips guys!!

I just ordered a rebuild kit. 

The lever was harder before then I disassembled the master from the bike and reinstalled it.  Now the lever has absolutely no feel just flops to the bar.  Very strange.

[the technological J]

 as long as your not seeing any brake fluid outside the system i think the rebuild should be a fix..... make sure u take special note of the placement of the rubbers in the cylinder because i didnt and ruined a rebuild kit

[honda rider#1]

try running a tube from bleeeder into a jar of brake fluid so you don't suck air bac k into brake system

[Hush]

Hmm I like the zip tie trick Rich, must try that on my old girl as I'm losing front braking on my twin discs.

[bollingball]

Try reverse bleeding. Put zip tie on same way remove fluid from master get 6" of clear tubing that will fit real snug over bleeder get 50cc syringe from vet or drug store fill with fluid hook syringe and tube to bleeder open bleeder a little push fluid in tighten bleeder bubbles like to go up not down. You can use your wife's turkey baster May take larger syringe

[Kevin400F]

Pushing fluid into the caliper bleed up through the hoses and into the master cylinder works well, but you need to leave the lever in the "released" position, NOT zip-tied to the grip.

[malcolmgb]

I had the same problem with my Harley, Bleed the brakes and could not get hard grip.

Saw a tip on the internet, Cable tie your brake lever to your grip and leave your brakes fully on over night...  all the tiny bubbles rise slowly rise and in the morning... nice firm brake!!

Just make sure your reservoir is full...

I did this for a couple of nights... work very well...

Guess similar to Hush's suggestion, but just in reverse...

Cheers

Rich

Can I just add this tip does not remove the air but forces the fluid to absorb the air, yes you get what feels like a hard lever but the fluid is contaminated with air, similar to fluid that has been in the system for years. Maybe completely bleeding the system after with fresh fluid is an idea but I wouldn't trust it if you are a hard braker.

[bollingball]

Kev I think you are correct it would probably block one hole. Mal please explain how would sitting over night force air into the fluid? not saying your wrong but I don't see how that would happen

[malcolmgb]

It's the putting under pressure of the fluid and trapped air for a long period. I was taught that as a mechanic at a company who were involved in motorsport. I believe air contamination is also the reason manufacturers recommend fluid is changed at regular intervals.

[Kevin400F]

My theory of why the "tie the brake lever to the grip" trick works is this: Since the pressure squeezes the air bubble to a tiny fraction of the "static" bubble size (probably by a factor of 10 to 20 or more), the tiny little air bubble is much more likely to migrate through fittings and so forth, and make its way up to the master cylinder where it is "burped" out of the recouperation hole on the first stroke of the lever. 

The same "amount" of air is in the line, but instead of a big bubble touching the brake line wall all around, it becomes a tiny ball of air only hitting the wall in a area of a few thousanths of an inch, and off it goes up through the line.

Kevin

[bollingball]

Kev I see what you mean now. I guess you could tap on the hose with a screw driver handle every couple of hours. In case the bubbles stick to the side walls like in a beer bottle Going4speed are you getting all this?

[brianmac]

dude, i had an old yamaha last month, the brake lines was full of crystalized brake fluid, i used brake fluid, and solid copper electric wire to ream out the crap, make sure you round off the tip of the wire, or you may damage brake hose. use compressed air to blow it out after u get it thru. patience, and autozone will loan you a vacuum bleeder for free.  make sure you put teflon pipe tape around the nipple threads and screw it all the way into the caliper and come back a quarter turn or less. bleed away, should take like 5 seconds, the only way to do cycle brakes.  keep pouring new fluid till it flows clear, and do it again after a few rides.

[going4speed]

I am but dang 403 ways to bleed brakes I only tried 3...only 400 to go!!! 

I think it sounds like I need to rebuild the master and go from there.  That will only leave 399 things left to try.

Kev I see what you mean now. I guess you could tap on the hose with a screw driver handle every couple of hours. In case the bubbles stick to the side walls like in a beer bottle Going4speed are you getting all this?

[Spanner 1]

OP... in order for brake fluid to flow down to the caliper from the master cylinder the front ( nearest the outlet, bango bolt, end ) hole in the m/c must be clear. This hole is 'ahead' of the piston/seal and is the only route for fluid to enter the brake line and down to fill the caliper. This feed hole is extremly small and blocks easily/ readily and must be verified clear to fill the system. Use the smallest needle from a sewing needle set to poke down thru' the hole. Do not pull the brake lever with the needle inserted or you will tear the seal on the protruding needle tip in the cyl. BTW... don't be tempted to use anything but the smallest point to open the hole, or brake performance will be affected ( with the tiny hole enlarged ). Be patient, the hole can be stubbornly blocked  : ... then ondo the bango bolt, pump the lever and verify fluid is leaving the m/c.... good luck.  While I'm at it  , when bleeding your front brake, the lever should not be pulled all the way to the handlebar, but only to about 3/4 " from it... why?, because past that point you are sending the piston/seal further into the 'unfamiliar' part of the m/c bore which will have some oxidation ( rough surface )  on it due to the piston never going that far when braking the bike and the effect on the smooth seal..... 

[going4speed]

Oh never thought about the travel going 'where no piston has been before' 

Rebuild kit will hopefully be here next week before the weekend.

I do have fluid down to the caliper.  The brake was working but it was super sponge bob square pants.

Thanks for the tips.

OP... in order for brake fluid to flow down to the caliper from the master cylinder the front ( nearest the outlet, bango bolt, end ) hole in the m/c must be clear. This hole is 'ahead' of the piston/seal and is the only route for fluid to enter the brake line and down to fill the caliper. This feed hole is extremly small and blocks easily/ readily and must be verified clear to fill the system. Use the smallest needle from a sewing needle set to poke down thru' the hole. Do not pull the brake lever with the needle inserted or you will tear the seal on the protruding needle tip in the cyl. BTW... don't be tempted to use anything but the smallest point to open the hole, or brake performance will be affected ( with the tiny hole enlarged ). Be patient, the hole can be stubbornly blocked  : ... then ondo the bango bolt, pump the lever and verify fluid is leaving the m/c.... good luck.  While I'm at it  , when bleeding your front brake, the lever should not be pulled all the way to the handlebar, but only to about 3/4 " from it... why?, because past that point you are sending the piston/seal further into the 'unfamiliar' part of the m/c bore which will have some oxidation ( rough surface )  on it due to the piston never going that far when braking the bike and the effect on the smooth seal.....