07 gsxr 600 brake problem

[whitetrash982]

hey guys , been a long time since i been here , but i got a bike again...couldent help it , im hooked!

anyways , after i ride for a while , say a 1\2 hour or so , and the brakes are nice and warm (no its not brake fade, i know how to ride) the lever starts gettin squishy, i already flushed out the front and rear brakes (yes with dot 4 as the manual and cap says) and still same thing, its got almost 9000 miles , someone already pad slapped the rear and theres hot spots all over the rear rotor , but the front rotors are fine and so are the pads , but they do squeek a little bit. anyways, i was curious as to what you guys think, im a professional auto mechanic , but i dont know much about bikes. oponions? thanks

[MagicRat]

Was the fluid from a new, sealed container?

My first thought is moisture is in the system, it turns to vapor when warm, duplicating the effect of air in the system. Another drain and fill might fix it.

[BP2K2Max]

have you tried bleeding the master cylinder?

[jeffcoslacker]

Disc brake getting soft with no obvious hydraulic issue I'd suspect either the caliper is getting stuck if a sliding type design, or something more sinister like a ballooning brake hose that's fixing to fail.

Some newer bikes use a floating disc design too and can cause weird problems.

Is it just the rear or both? You could have a hose failing in a way that it's holding hydro pressure, dragging the brake AND overheating the fluid, which will also make the pedal/lever go soft. Sounds likely with your heat spotted rotor.

Those short little hoses on the rear can get damaged easy if someone tried to remove the caliper to do the pads, and didn't take the hose and line out of their hold downs so they didn't have to twist or stretch the hose.

Just like a car, you can usually diagnose a hose holding pressure pretty easy. Ride it until the brake gets hot, then open the bleeder screw a bit. If it fires off a big shot of pressurized fluid with no pedal/lever applied, it's defective and making it drag...fluid should just drool out when opened if everything is normal...a sticking sliding caliper won't do that either.

[whitetrash982]

its actually the front brakes that are going squishy when hot. i just htought id say the rear was spotted to signify whta kinda rider whom ever had it before was. however , the caliper hangin up sounds like it could be the culprit, the fronts look a bit rusty, and i could see it getting hot (and consequently a little bigger) and hanging up. the brake lines look ok , and i flushed the crap out of the master and both calipers, withbrand new fluid out of a new can. but i think ill go take off the calipers and pull the pads, clean out the rust, check the piston movment and lube everything up a bit. thanks for the advice guys , ill let you know what happens.

[jeffcoslacker]

Piston movement is important, but sliding/pivoting action is just as important if it uses a sliding style caliper...don't know what yours uses, may be all pistons from both sides of the rotor...

I've had a helluva time getting front brakes on bikes to bleed completely...I taught myslef a pretty good trick though that works well. Same theory as a speed bleeder, but I don't have one of those...

I just take the bleeder screw out and push my thumb tightly over the hole, and pump the lever like mad with my other hand, letting fluid and air blow out from around my thumb but keeping it pressed down tight enough to keep air out.

After it stops spitting air, I replace the screw and bleed a couple of pumps just to clear the screw bore...done.

[whitetrash982]

well , its gotten a little better since i cleaned out and lubed the front brakes , but still gets a bit squishy , and im anal retentive with my stuff. so i think i might take the pistions out (unfortuantly, all 8) and clean them out real good , but before i do that , im gonna check the runout on the rotors , i was thinkin about that, if a rotors warped , but its a floating rotor , it may just be pushing the pads back in a little creating this effect ,which would be compounded by heat

and jeffco, much eaiser way to do it then that... grab a empty 1 liter bottle and rip the label off and a few feet of clear tube that will fit over the bleeder nipple. poke a hole in the bottle cap and insert tube. put a wrench of the bleeder and the tube over it. loosen bleeder and flush to your hearts content, youll be able to see all air coming out in the bottle, or the tube. and when done , just close the bleeder

[jeffcoslacker]

Originally Posted by whitetrash982

well , its gotten a little better since i cleaned out and lubed the front brakes , but still gets a bit squishy , and im anal retentive with my stuff. so i think i might take the pistions out (unfortuantly, all 8) and clean them out real good , but before i do that , im gonna check the runout on the rotors , i was thinkin about that, if a rotors warped , but its a floating rotor , it may just be pushing the pads back in a little creating this effect ,which would be compounded by heat

and jeffco, much eaiser way to do it then that... grab a empty 1 liter bottle and rip the label off and a few feet of clear tube that will fit over the bleeder nipple. poke a hole in the bottle cap and insert tube. put a wrench of the bleeder and the tube over it. loosen bleeder and flush to your hearts content, youll be able to see all air coming out in the bottle, or the tube. and when done , just close the bleeder

Yeah I've done the one man bleeder setup before, but for some reason with trouble bike bleeds the key seems for some reason to be rapid pumping...which will draw bubbles back in with that setup. Otherwise, it's great

[richtazz]

I have a hand vacuum pump with a bleeder kit that is the cat's a$$ for troublesome trapped air. I got it at harbor freight for about $25-$30.

[whitetrash982]

Originally Posted by richtazz

I have a hand vacuum pump with a bleeder kit that is the cat's a$$ for troublesome trapped air. I got it at harbor freight for about $25-$30.

i already have a blue point vacumm gun with a bleeder attachment , but ive never liked using vacumm to flush brakes. something about it just never struck me and working well , and i always end up have to pressure bleed it anyways , thanks for the idea though