f4stunna

i changed my rear brake pads a few days ago. there was there was absoluty no pad left and i started hitting the backing, so when i put them in i had to spread the caliper like crazy. before i changed them, the brake engaged almost immeditally. then after i changed em the pedal would go down almost all the way with almost no pressure and wouldnt lock the tire. since then i bleed through a bottle and a half of brake fluid (pumping the lever to build up pressure then crack and tighten the bleeder valve and repeating). the problem is now the pedal will go down like half way and there isnt that much pressure but if i pump em it will build up. like say im coasting along at like 20, if i pump it a lil then push down the brake all the way it will just slow the bike down til im almost stopped then lock it. im puzzled cuase it should have gotten better. i need help.


sorry for the long post too.

f4rider

yeah, it should have gotten better

Mikie

You're just gonna have to keep bleeding it. Make sure all bolts are snug, and there isnt a crack in the line.

f4stunna

i donno. im still lost. i bleed through a whole bottle again today and it got a little bit better but im not sure if if its cuase i cleaned everything with brake cleaner or not. but while bleeding it there wasnt a single air bubble. but its still no where near what it should be

Mikie

You can always try reverse bleeding. Get a syringe filled with brake fluid, pump it into the caliper through the bleeding outlet with the cap off the reservior.

MattMingay

try bleeding it from all bolt banjo fittings plus bleeder starting with closest to lever. sometimes air gets stuck in fitting.

f4stunna

how do you bleed it from the banjo bolts?

Tdeal28

The banjo bolt on the master cylinder most likley need to be bleed. Just pump the crap out of the pedal, but instead of bleeding from the calpier bleeder screw...Bleed from the banjo bolt on the master cyclinder. Just crack it open like the caliper screw and do that a few times until you get no air and a good flow of brake fluid.....Then go to the brake caliper bleeder screw and bleed the brakes from there..

f4stunna

how are you going to be able to tell anything by doing that as far as getting good flow of fluid, isnt it just going to be pouring everywhere?

MR. RYAN SMITH

That Is Your Problem. Get A Rag And A Wrench, Pump Then Crack The Banjo And Retighten It. Only A Small Amount Of Brake Fluid Will Come Out, But Will Definately Get The Air Out Of The System. Do The Banjo At The Master, Do The Banjo At The Caliper And Then The Bleeder Valve Last.

f4stunna

alright, ill try that sometime this week and see if it makes a difference.

f4stunna

ive bleed through another bottle. 4-5 resivior fulls from the banjo on the master, the banjo on the caliper and then bleed it from the caliper. i can lock the tire now, but it still is all mushy and sucks *** and the pedal goes almost all the way down still.

i cant figure it out. ive had one person tell me that i need to have someone with a vacum bleeder thing that hooks up to a compressor to do it cuase it will suck the air out. i also had another person tell me that i need to check the o-rings in the system cuase thats what it could be??

just want some more advice before i go and tear the whole brake system apart and make one hell of a mess doin it.

rrmike

Your master cylinder is probably junk. If you can pump the brakes up and get them to work good I'd try that (changing the master).

That's the way it's always been on cars I've had. I have always done my own work on them but never had a problem (other than crash damage ) on my 954 so I don't know if bikes are the same way. It sounds like bleeding isn't doing any good.

It does seem coincidental that it would go bad right when you were changing the rear brakes though. Maybe when you pried the calipers open if you didn't have the bleeder open it forced brake fluid back into the master and damaged the seals or something.

It's at least something to consider since no one has mentioned it.

for what it's worth

f4stunna

is there anyway i can test out if its the master or not? or just go test it out with another one on the system?

the reason why i dont think its the master is it still works, just badly. like it feels like there air in it, but if i pump it alot it will build up pressure. but if i let it sit for a while it loses it again. i can lock the tire goin like 40, but i need to pump it a little first. it just feels mushy like theres air in there.

and where are all the o rings at in the system?? and does anyone know what size they are? i was thinking i can go get a few now and just change em all and see what difference that makes.

rrmike

Like I said I don't know a great deal about the master cylinders on bikes but on cars that's how they work. They don't just fail to work at all but the seals get bad and you have to pump them to get brake pressure. It acts a lot like air in the lines. It's the most expensive thing to try I'm sure so I'd wait until you had exhausted every other possibility but I just wanted to give you another possible cause.

Maybe you can rebuild them and that's what they're talking about with the o-rings. Either the master or the caliper. I don't know of any other o-rings in the system but I'm not a graduate of mmi either

Hope you figure it out bro. If not go to the "954 Q&A" thread and ask KungFu954 there. He's an awesome motorcycle mechanic and is one of the nicest guys I've ever met on the net. He may or may not know as much about F4's as he does about 954's but I'd bet they're all pretty similar and he will have some ideas of exactly what you should try in what order to fix the problem.

f4stunna

anyone know what size o rings i need??? im thinking about just taking the whole system apart and changing em just to see if it helps. i think it'd be better to already have em than to take it apart then go to the store and match em up.

Z-UNIT

anthony was looking at it and he said the line going from ur rear brake res to ur master is kinked....unkink it and it shud bleed the air out thats trapped in there

f4stunna

i already tried that before i bleed it from the banjos

e-Roc

just a question. When you get on the brakes hard and let off does it imediately disengage the pads or do the pads still scrape for a little bit?

f4stunna

it lets go right away