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Discussion Starter #1
Recently got home from Iraq. And the brakes were mush. I got new fluid and bled all the old stuff out. Done this twice so far. After sitting for maybe a week they get soft again. I mean i'm pulling the lever to the throttle with minimal effort. Didn't check it this last time to see if there's air again in the system, but thats what it feels like. Anyone else ever have this issue? I checked for leaks and calipers dont look like they're stuck. I'm wondering if the master is starting to go....
 

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Mine does it also over time. Last time I bled the brakes there was quite a bit of air. Can't figure it out, no leaks anywhere, etc. I just bleed it more often and no problems.
 

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hi bud you didnt say if you have braided brake lines but it sounds like you have air in the system or one of the brake pistons might be stuck in the caliper so your breaks would feel spongy as hell had the same prob on my suzuki tls1000 stripped the caliper and all was well hope this helps

chris
 

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Discussion Starter #4
stock lines right now. thing is if theres air in the lines how the hell did it get there if I don't see any leaks? But I'm gonna check first and see then I'll post the results.
 

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over time the stock lines start to let in the elements try braided lines
I've got those already, and, for the record I had a '78 Honda motorcycle that had the stock rubber lines on it for 25 years before I ever changed them only due to their age and I never had a problem with air getting in that system. So, how much "time" are we talking here....?
 

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Braided line are about resisting expansion a tad more than the rubber ones, because of the steel braided jacket, not about preventing leaks or admitting less air. The connections are same banjos. I have a 20 year old Kawasaki still with the original rubber lines and brakes are stiff.
 

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Do you have enough fluid in the reservoir? There is the possibility that there is enough fluid when the master cylinder is level, but when you set the bike on the kick stand or lean while riding, the fluid goes to the opposite side of the reservoir than the MC fluid pickup hole.

But you probably have a bad master cylinder.
 

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sorry guy should have said im over in scotland and the weather is **** over her at the best of times the stock hoses on my tl1000s were fooked after about 4 years .

try cracking the top banjo bolt when squeezing the brake lever sometimes you can get a build up of bubbles their
 

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Do you have enough fluid in the reservoir? There is the possibility that there is enough fluid when the master cylinder is level, but when you set the bike on the kick stand or lean while riding, the fluid goes to the opposite side of the reservoir than the MC fluid pickup hole.

But you probably have a bad master cylinder.
Agreed.
 

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Discussion Starter #11
Ok bled it today. Started at the master and holy crap nothin but air came out. But brakes work again. Still though not sure why it does it. No leaks. Now I do have a question for you guys. I upgraded the fluid from dot4 to dot5. Could this be an issue? Maybe a chemical reaction causing air? And yes the reservoir is full.
 

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Alrighty then, time for my hydraulics hat [on] - with DOT grade hydraulic fluids, you really can not "upgrade" by going up in the number. That number represents the chemical properties of the fluid only. If you are trying to "upgrade" the fluid, the thing you want to do is find a fluid that has a higher flashpoint, less tendency to boil, etc. Simply going from DOT 3 to 4, or 4 to 5 is not going to do anything for you. What the DOT 5 fluid CAN do however, is potentially eat up the seals in your DOT 4 system.
 

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Ok bled it today. Started at the master and holy crap nothin but air came out. But brakes work again. Still though not sure why it does it. No leaks. Now I do have a question for you guys. I upgraded the fluid from dot4 to dot5. Could this be an issue? Maybe a chemical reaction causing air? And yes the reservoir is full.
Do you mean DOT 5 or DOT 5.1? DOT 5.1 is compatible with DOT 4 and won't cause any problems. But DOT 5 is synthetic and not compatible and will cause problems as Compstall pointed out. I think DOT 5 (synthetic) is only compatible with a few bike makes, I think Harley but not 100% sure.
 

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Discussion Starter #15
Actually it was 5.1. The other stuff is for Harleys.
uglymutt- Why not use 5.1? Its compatible. I understand I might not need it but it should work.
Now what makes me think is this all started when it did have dot4 in it. I got back after a year away and the brakes felt just as they feel now. Not to disagree with you uglymutt but I got a feeling going back to dot4 will not make a difference.
Oh and yeah yesterday they were already pretty much mush again. Thats after 2 days after bleeding. I would throw a master at it but its obviously got air in it. I'm going to take apart everything and start looking again for an answer.
 

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i would replace all the brass washers on the lines and the bleed nipples
its possible for the system to suck in air through the washers but not leak

failing that its a master cylinder imo
 

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Discussion Starter #17
So I went in today to buy a few things for the bike to fix my issue and was told that my problem is a common one apparently. Bad design or something with the master cyclinder that has no apparent leak but still lets air in. What I was told was that this same master has been used for years not only on kawasaki but suzuki. So now the its rebuild the master and hope it goes away or buy an aftermarket one.
 

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Commonly overlooked brake maintenance item - brake piston seals. If they harden or crack, the pistons don't move as well as they used to and air can be introduced.

Don't forget them.
 

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Sorry I forgot to look at this thread.

“Ideally, silicone fluid (DOT 5) should be used only to fill non-ABS systems that have not been previously filled with glycol based fluid (DOT 4). Any system that has used glycol based fluid will contain moisture; glycol fluid disperses the moisture throughout the system and contains corrosion inhibitors. Silicone fluid does not allow moisture to enter the system, but does not disperse any that is already there either."

You get a pocket of water you can't bleed out without flushing the whole system and putting DOT 4 back in.

About the DOT system in general. DOT 5 is not better than DOT 4. It’s a different fluid with different properties designed to work in a DOT 5 system. You won’t have any gains from using it and potentially it can hurt your whole system by corroding components or things like that I think but mainly moisture issues. The best upgrade to fluid is to use fresh fluid from a new sealed container. Brake fluid soaks up moisture from the air as soon as it’s opened and relatively fast. That decreases the density and can give you swishy brakes. They do sell fluid that is compatible with multiple systems but I stay away from any universal fluid. Just like I wouldn’t use universal coolant on an Audi or VW that uses G4 (pink). Some say you can but I think that that they make things for a reason. A lot of time and money goes into the design of fluid systems so it’s best to abide by the standard.

Who knows you may never have a problem but by the way it sounds you do have a problem and if you’re going to flush the whole system anyway I would refill with DOT 4.
All this aside the boiling point of DOT4 is 446 degrees F. If you can bring that to boil you are my hero.

Look here is you want more info.
http://en.wikipedia.org/wiki/Brake_fluid
 
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