spongy front brakes?

[dingo]

hi guys, i have bled my front brakes to no end and they are still spongy, just let it all drain out. any idea what to run through the brake system to clean it out before i try again? or anyone elses solution to this problem if theyve had it?
Cheers
Carl

[BANDITROD]

do you have braided lines yes or no and what type of fluid are you using mate

[dingo]

hi BANDITROD ,yes braided on the front, havnt got to the rear yet but they are also spongy, using cheap ass nulon super dot 4 i need to get some more tomorro so whatever you recommend i shall get. i will try clean it all out tonite ready for tomorro.
Cheers
Carl

[DiscoDan]

the quality of the fluid won't effect how the brakes feel initially but will effect how much moisture it absorbs over time and how it reacts to overheating under repeated heavy braking. There's nothing better to flush with than more brake fluid. Depending on the bike it sounds like there's still air in there somewhere. I've never had to do it but apparently strapping on the brake lever overnight will let air bubbles float up the line and out the bleed hole, not sure if anyone else can verify that?

[dingo]

will run some more fluid through and try that, maybe its a seal, the brakes are there but i wouldnt take it on the road, the lever can be pulled to the grip.

Carl

[BANDITROD]

yeah i have heard of that before use a cablie tie to pull lever in to the bars and even try flicking the brake line like the doctors do to get air out of needles if you konw i mean

Use a syringe and push the fluid through from nipple to mc

[dingo]

go down to the shops now , run 1/2 a ltr through it and do the zippy trick.

Carl

[Weaselman]

instead of pumping the leaver just move it in little strokes then full strokes with the bleed nipple shut.
You often get alot of bubbles comeout the top

[dingo]

will try that too , just flushing em out now.
Cheers for your quick helpful suggestions guys[8D]

Carl

[dingo]

flushed and bled over 600ml through both lines , to the best i know how (never failed me before,not like this), there is hard preasure on the discs but the lever still hits the handle, will try the zippy trick over night:(

[BANDITROD]

yeah there is def still air in there somewhere mate have you ever tried using a syringe at all you go to your local pet stock shop and get one of those big fuckers and use it to pump fluid from the bottom up garranteed to get rid of all air in the system but see if the cable tied lever works first

[dingo]

i used a syringe to suck it out , i got a 60ml to initially push it up but i didnt think it would hold enough fluid to do it in one hit. see how this goes, was going to try push it with a bike pump , but not seing inside it worried me bout more bubbles. will go on the hunt for a larger syringe tomorro.

Cheers
Carl

[WATEVR]

mate have you bleed the master cylinder with out the lines connected up??

if not do so with your thumb over the bolt hole then bleed the rest of the system after that is done do so with the lines bolted up.

[OLD SKOOL BANDIT]

If all that fails, try servicing the calipers. May have a build up of crap on pistons. Also fuct washers on banjos, (If you have replaced lines).

[Docktor]

Remove the sponge and try again ?

Best way is with a syringe ya can get from a vet, they got huge fuckers for horses. push the fluid up to the master, dont bother tryin to suck the air down to the callipers

[crazymofo]

im with old skool on this, service the calipers, then grab some clear hose, 2 containers holding some water in them, crack the nipples. fit the clear hoses and put the other end in the water (this is so the calipers cant draw air back into the system) leave the nipples open and pump the fluid thru till the clear lines show fluid in both.

close the nipples, leaving the hoses attached, pump the leaver, hold in then crack the nipple on each side alternitivly. you'll see the air coming thru, keep doing it till the leaver feels good to you.

cheers.joe.

[dingo]

quote:Originally posted by Docktor

Remove the sponge and try again ?


haha, i was wondering how long and if that would come up[8D]

went to town today and got a master cyl. kit more fluid and some new copper washers, stripped the calipers and will clean the entire setup and start again.
thanks again for the support and tips , will let you know how it goes :)

[Tony OW31]

I used to have this problem regularly, especially when putting braided hoses on, got myself a mightyvac, now it's a 5 minute job, and no more problems.

[OZ750L]

Try the zippy trick. It does work. Tony, Docktor and banditrod have the best idea with there info. Don't forget to crack each banjo and purge the air out of them. Water cleanup. Try Motul 4.1.

[dingo]

there must be an issue somewhere, done everything as suggested and the lever still hits the handle, the only thing i found sus was a small patch of pitting (like 2mm round) on one piston , there seems to be no fluid leaking anywhere. i will keep looking and playing. :(

[dingo]

looking like there may be some issue with the braided lines, got an other full set of brakes to put on till after rego. will diagnose the problem and let you all know what it is , thank you all for your help :)
Cheers
Carl

[BANDITROD]

what breed of braided lines are they mate

[dingo]

i couldnt tell you sorry BANDITROD , prob get a pic if you want , they look old

[BANDITROD]

yeah post up a pic and also just out of curiosity what number do you have your lever adjustment set at

[dingo]

sorting out a pic now, even with the lever set 1/2 way between numbers still the same

[BANDITROD]

mmmmmm ok lets see some pics and we will see if we can help ya out mate

[dingo]

http://www.streetfighters.com.au/forum/upload/14841572575099.JPG

can get closer if you need

[BANDITROD]

have you been doing this on or off the bike...i mean were they fitted while you were trying to bleed them up

[dingo]

on the bike, i only just now ripped em off, mate told me i can use his old setup for a while , got a spare clipon
so i figure i will try trouble shoot while they were off

[BANDITROD]

ahh ok cos if you were trying with them off put something roughly the same thickness of you disc in between brake pads otherwise your pistons will come out too far i think

[dingo]

got some alloy to throw in there, it only builds up so much preasure so i cant even squeeze the shit out of it and zippy it to see where
fluid is getting out, got brand new pads in there atm

[Harry]

hi dingo, those brakes are the same set up as mine and i had the same problem: first of all split the calipers and take to the pistons that push on the pads with some fine wet and dry try 400 grit and get the years of road grim off em,dont push em all the way out or you'll be after a G clamp to get em back in,braided lines are a good move but make sure you have it all the way from the lever, old rubber is a bitch,you can feel it expand or worse see it.
still no luck..you may need to re-kit the master cyclinder and bleed em up but that is the lot they should work fine :)

[dingo]

i just put a kit in the master and i stripped the whole setup and hit the pistons with 2000 W/D , i didnt get new piston seals but i will sort some out before they go back on, they seemed to seal very well. this bike has been sitting in a shed for bout 2-3 years , im just bringing it back to life.

[Harry]

wot sort of bike is mate............i'll go if ding go's hahaha

[dingo]

long time since i heard that album :) , its an 88 gsxr 750

[dingo]

quote:Originally posted by Harry

wot sort of bike is mate
click on my name then click the pic, link to the bike in there,
parent directoy is a young mates site of some nice pictures he sells ,
budding photographer....plug plug :)

[dingo]

excuse the tripple post, those in the know scottymac has been helping me and it has him stumpped too

[OZ750L]

Dingo,

Are you losing pressure or is the fluid level dropping as well? Check it's not bleeding back past the seals in the master cylinder. Did you lightly hone the master cylinder before installing the new kit? Just need to break the glaze with about 800 or 1000 W/D. Otherwise, bite the bullet and get in stainless sleeved.

Couple things to try. Drop the fluid level in the M/C reserviour to about half, put the calipers up higher than the m/c and set them up with clear plastic tubes on the bleed nipples looped up and over and down into a catch can. Get some pressure on the m/c and crack the bleeds one at a time while holding pressure in the m/c to get a standing column of fluid in each tube. Then, leaving the m/c alone and keeping it lower than the calipers, barely crack the bleeder on 1 caliper and using a flat bar or similar or a clamp, force the pistons on one side of the caliper back in until they bottom. Should force fluid and any trapped air up the tube. Don't panic about it sucking air back in because the standing column of fluid is there to prevent it. Do the same to the other side of that caliper and then lock off the bleed screw. Repeat the same procedure on the other caliper.

When you've finished doing that to the calipers, lift the m/c above them and top it off with fluid. Make sure the cap is back on tight. Get a bucket of water, a cup and a few wet rags. Gunna need to wash off any spilled fluid. Put something in the calipers to try to hold the pistons at their bottomed out position. Crack the banjo at the m/c and nip it back up. Pump the lever and get some pressure, should come up straight away, then crack the banjo slightly while holding pressure on the lever. Tighten it back up before all the pressure bleeds off. Repeat a couple of times until no bubbles pass the banjo. After you are sure you have got all the air out to this stage, pump the lever up until you have pressure and then zip tie it to the bar for a few hours then repeat the bleed process at the m/c banjo.

When you have done all this, put a 8mm spacer between the pads and pump up the brakes, topping off the m/c as you go. When the pads have clamped up, check the system by doing 2 or 3 bleeds on each caliper. Everything should be good by this stage and the lever should only travel about 1/4 to 1/3 of the way in to the bar.

If not, repeat.

If not still, I'm buggered if I know. Replace them with another set maybe? Or syringe them from the bleeders up to the m/c with new fluid.

Hope this gets you outta troble.

[scotty mac]

i've given dingo a stock set of brakes with rubber lines to try. then its jus a prosess of elimination changing parts 1 by 1.

[OZ750L]

Scotty, good idea. Takes a while though.

Know what you are going through. Have a 82 GPz1100 that had brake issues. Turned out to be the slider pins had ovalled the housing and were allowing the calipers to rock and caused the lever to go spongey. Only picked it up when I was talking to a mate who is a bike mechanic and he told me that the GPzs had had issues with that in the past and how to check it.

[dingo]

todays efforts :( , started off by replacing my braided lines with a 3 part rubber set, bled the absolute crap out of everything , still the same, swapped calipers one at a time bleeding after each, still the same , swapped masters, got a little better , kept bleeding all points (tell ya i should have got a 20ltr drum, been keeping the good stuff)it now holds some stiffness, but not like it should, i can still pull the lever to the grip. figured thats gunna have to do:(, went to work on my set and did everything in OZ's description to a T , even redone the master , they are still the same. i shall buy some new seals , Orings and bleeders for the calipers and try again. had quite a few MX bikes and cars and never have i had this much drama with brakes :(

[BANDITROD]

keep in mind mate that when you go for a ride they will stiffen up due to the temp of the fluid once it warms up the will prob feel alot better

[dingo]

thats what scotty said, his setup feels ok on there now , try take it for a strap on the weekend, see how it goes. such a simple task and what a drama O_0 , cheers for all your help guys.
Carl

[80s freak]

Is it the correct lever for that master cylinder. Seen that screw a few people over. Another option is to by a vacuum bleeder. Should be able to get one from your local bike shop. I think a M.C.S. Do them. Not sure on cost. So you suck the fluid out through the calipers.

[dingo]

i did think about the lever, it seems to feel more comfortable sitting 1/2 way between numbers on the adjuster but ive been swapping the same lever between brake sets and it works fine on this M/C , may look into another.
Cheers
Carl

[dingo]

to all that helped me on this a big thankyou , got it rego'd , the guy was still a bit hesitent but he let me go , mucked around heaps since then and even put my own brakes back on , it must be the lever cos i placed a small nut on the pin between the adjustment mechanism and the are sweet as now , will do till i buy another one. when i get around to putting some fat bars on is it a wise move to just extend the hoses via a tripple banjo fitting into a single line to my M/C or is this a bad idea ???
thanks again guys
Carl