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post #1 of 7 (permalink) Old 08-31-2007, 12:17 PM Thread Starter
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Mushy brakes?

Alright... here goes.

'97 Monster 750. Dual front brake conversion (done by previous owner) using a junction block bolted to upper triple (looks stock from a 900 maybe?).

After changing over to clip-ons I bled my brakes and have been having some trouble ever since (actually I've now bled them three times, LOL).

Brake lever takes a long time to "pump-up" while bleeding. As in I bleed, then the lever travel is long and after about 20 strokes it comes back to where it should be. I've bled it manually (squeeze lever, open bleeder, close bleeder release lever). I've back bled it (forcing fluid from the caliper up) and I've used a vacula (sucker) to bleed from the caliper down. I've done it with the brake lever pulled in and out. One would think I've gotten all the air out.

They symptoms: Brake lever pull is randomly different. I'll leave the house in the morning and have a great lever all the way to work. Then I leave for a ride after work and get a lever that's slightly closer to the bars under full stop. Then I'll run a good pace through the hills and pull to a stop light to get a lever that barely takes any pull to apply brakes. The lever never really feels squishy and once it contacts it doesn't get closer to the bar (like fluid bypassing in the master).

The bike has new pads and upon installation I inspected the calipers. Everything is clean and working smoothly.

So what gives. I feel like there's still air in the lines, but I can't imagine how. I've bled it every possible direction. I've got a track day next weekend and want to make sure that I don't end up with a master cylinder failure. How long do the coffin masters last? Is this a common failure, or does it sound like I'm on the wrong track?

Thanks in advance guys. I appreciate any input or wisdom.
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post #2 of 7 (permalink) Old 08-31-2007, 05:05 PM Thread Starter
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Re: Mushy brakes?

really? nothing?

I'm going to pick-up some adjustable levers and give them a try. Hopefully I'll get a bunch more miles before next weekend. I'll be bummed if I have brake problems at the track.

-Evan
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post #3 of 7 (permalink) Old 08-31-2007, 05:09 PM
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Re: Mushy brakes?

sounds to me like you have a leak somewhere letting air into the system.
maybe check the banjo bolt connections, re-tighten with some teflon tape around them?

(oh and then you get to bleed again :P)
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post #4 of 7 (permalink) Old 08-31-2007, 05:12 PM
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Re: Mushy brakes?

If it's air in the lines, you can often quickly pump the lever five or six times and it will firm up for a while. That's how the brakes on my ST2 have been just about the full four years that I've owned it. However, they've firmed up a bit lately, possibly related to pushing the pads back in when I put the last front tire on it.

If you're interested in doing a brake bleeding session Monday morning (Labor Day), I would be up for that, since you only live a few miles away. I really should bleed the brakes on both of my bikes.
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post #5 of 7 (permalink) Old 08-31-2007, 11:17 PM
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Re: Mushy brakes?

Have you tried to bleed the air out of the banjo (or bleeder if you got one) on the master?

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post #6 of 7 (permalink) Old 09-04-2007, 11:36 AM Thread Starter
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Re: Mushy brakes?

Sorry Scott.... Didn't even fire the computer this weekend. Otherwise I might have been interested. I've got a vacuum bleeder at my house if you're interested in using it.

I bled again (4th time) and the lever is feeling good right now. It felt good last time till I took it on a long ride, though, so we'll see what happens. I've tried bleeding at the banjo bolts. My only concern is that I haven't replaced my banjo seal rings when I loosened the lines. I know it's a no-no, but I didn't have any handy. I've yet to see air leak into the lines at the fittings when fluid isn't leaking out. I suppose it's possible though (as air is thinner than fluid).

We'll see what happens this time.
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post #7 of 7 (permalink) Old 09-04-2007, 11:50 AM
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Re: Mushy brakes?

if this keeps happening, even with the bleeding you're still doing, you may have a bad MC.

do you have the coffin style MCs on your 750? i don't know what type of MC your bike had.

the coffins are apparently known to fail in this manner. mine did and i replaced it with an old goldline and the problem went away.



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