Spongy front break - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 11 (permalink) Old 06-13-2009, 12:26 AM Thread Starter
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Spongy front break

The front break on my 94 Vulcan has started to feel spongy when I apply firm break pressure. It gives and gives a little more but there still seems to be plenty of travel, but my breaks don't feel quite as strong as they should be especially for dual rotors.

A mechanic friend of mine thinks it's water in the break line and that some rubber components in the master cylinder and the calipers are probably rotted and need replaced. Is the problem that serious or will a simple break fluid change solve it?

1994 Kawasaki Vulcan 750 named Jinba Ittai (Japanese for "Horse and rider in perfect harmony").
Jardine Pipes
Splines Lubricated
Painted Instrument Bezels
Headlight Visor
Chrome engine guard
Leather Fork Bag (contents: Pressure gauge, tools, and a Book of Psalms)
Yuaso MF AGM Motocross battery
Kenda Kruz Front tire
Duro Boulevard rear tire

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post #2 of 11 (permalink) Old 06-13-2009, 01:38 AM
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Quote:
Originally Posted by VulcRider24 View Post
The front break on my 94 Vulcan has started to feel spongy when I apply firm break pressure. It gives and gives a little more but there still seems to be plenty of travel, but my breaks don't feel quite as strong as they should be especially for dual rotors.

A mechanic friend of mine thinks it's water in the break line and that some rubber components in the master cylinder and the calipers are probably rotted and need replaced. Is the problem that serious or will a simple break fluid change solve it?
Drain the system, repace the Master Cylinder seals and use Valvoline DOT4 Synthetic Brake Fluid.


85 VN700 "Old Yella"

REBUILT ENGINE
CUSTOM PAINT
VANCE & HINES CRUZERS
EAR SHAVED AND RE-JETTED W/K&N'S
DUNLOP ELITE K591 FRONT & REAR
VOLTMETER
SYNTHETIC BRAKE FLUID
SYNTHETIC OIL & GEAR LUBE
PLEXISTAR 2 WINDSHIELD
SPLINES LUBED
ACCT'S GREASED W/TOC SPRINGS
COASTERD
LEATHER SADDLE BAGS
LEATHER TOOL AND ROLL BAG
PICKUP COILS GAPPED AT .018"
NGK CAP, WIRES, IRIDUMS
BARNETT FRICTION PLATES & SPRINGS
CUSTOM GRIPS, MIRRORS, LEVERS
ORIGINAL STATOR & R/R 14.5v
DEKA MF AGM ETX15L

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post #3 of 11 (permalink) Old 06-13-2009, 08:32 AM
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Is your brake fluid a nice amber color or does it look more like muddy water?
Old brake fluid will produce spongy brakes. Simple enough to check if you just look at the sight glass on the front of your Master Cylinder.
Brake fluid should be changed every year or so since it does tend to pick up moisture even with good seals.

Dianna
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2000 VN750 Sere (Serendipity)
1990 GL1500 (Ole Blue)
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post #4 of 11 (permalink) Old 06-13-2009, 11:22 AM Thread Starter
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The fluid color is a darker amber/brown and no sign of muddyness at all.

Lance, what master cylinder seals exactly are you referring to? All of them? lol

1994 Kawasaki Vulcan 750 named Jinba Ittai (Japanese for "Horse and rider in perfect harmony").
Jardine Pipes
Splines Lubricated
Painted Instrument Bezels
Headlight Visor
Chrome engine guard
Leather Fork Bag (contents: Pressure gauge, tools, and a Book of Psalms)
Yuaso MF AGM Motocross battery
Kenda Kruz Front tire
Duro Boulevard rear tire

"Buy the ticket, take the ride."
-Hunter S. Thompson
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post #5 of 11 (permalink) Old 06-13-2009, 12:20 PM
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Quote:
Originally Posted by VulcRider24 View Post
The fluid color is a darker amber/brown and no sign of muddyness at all.

Lance, what master cylinder seals exactly are you referring to? All of them? lol
You have to buy the complete piston assembly, seals are not sold seperatly.


85 VN700 "Old Yella"

REBUILT ENGINE
CUSTOM PAINT
VANCE & HINES CRUZERS
EAR SHAVED AND RE-JETTED W/K&N'S
DUNLOP ELITE K591 FRONT & REAR
VOLTMETER
SYNTHETIC BRAKE FLUID
SYNTHETIC OIL & GEAR LUBE
PLEXISTAR 2 WINDSHIELD
SPLINES LUBED
ACCT'S GREASED W/TOC SPRINGS
COASTERD
LEATHER SADDLE BAGS
LEATHER TOOL AND ROLL BAG
PICKUP COILS GAPPED AT .018"
NGK CAP, WIRES, IRIDUMS
BARNETT FRICTION PLATES & SPRINGS
CUSTOM GRIPS, MIRRORS, LEVERS
ORIGINAL STATOR & R/R 14.5v
DEKA MF AGM ETX15L

Best Auto/Moto Insurance | Motorcycle Protection Today | FREE Trade-In Quote

Last edited by lance328; 06-14-2009 at 05:14 AM.
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post #6 of 11 (permalink) Old 06-13-2009, 10:38 PM
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Start with the brake fluid replacement. If that doesn't work, I can probably set you up with a working front m/c dirt cheap.

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post #7 of 11 (permalink) Old 06-14-2009, 09:42 AM
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Quote:
Originally Posted by VulcRider24 View Post
A mechanic friend of mine thinks it's water in the break line
Regular brake fluid is glycol based and hygroscopic, meaning it absorbs moisture. Humidity and weather conditions in your area determine how much and how fast and contributes to the color change from clear amber to muddy brown. Brakes fluid needs to be change about every 2 years on average (on all vechicles).

I do this on all my vehicles and it is like having brand new firm brakes.


Chris Glennon - Portland, OR
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post #8 of 11 (permalink) Old 06-27-2009, 09:18 PM Thread Starter
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Ok guys! After a brake fluid change my brakes feel much much more solid. The fluid was way past its prime. I had no idea new brake fluid was clear haha!

Thanks for the help!

1994 Kawasaki Vulcan 750 named Jinba Ittai (Japanese for "Horse and rider in perfect harmony").
Jardine Pipes
Splines Lubricated
Painted Instrument Bezels
Headlight Visor
Chrome engine guard
Leather Fork Bag (contents: Pressure gauge, tools, and a Book of Psalms)
Yuaso MF AGM Motocross battery
Kenda Kruz Front tire
Duro Boulevard rear tire

"Buy the ticket, take the ride."
-Hunter S. Thompson
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post #9 of 11 (permalink) Old 07-03-2009, 02:23 PM
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My Fluid looks like think chunky muddy water. I want to drain the system and completely remove it but the two screws are seized. I have been soaking them in PB plaster for a few weeks, i think i have to remove the resevoir from my bars and use an impact wrench because they screws are pretty mangled. Could I just use dot 3 since i have a whole bottle?

1986 Vn750
18,800 miles, and counting
Bone Stock
New cam chain tentioners
all fluids changed
Spline Lube
windshield
Engine Guard
B-stone S11 RWL-stock sizes
*wanted*
New grips

2001 Vn750
13,100 miles, and counting
spline lube
Bridgestone S11 100/90
Shinko 170/80
rear end oil change
aftermarket mirrors
windshield
otherwise all stock
*anticipated mods*
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post #10 of 11 (permalink) Old 07-03-2009, 02:47 PM
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They're really soft. The head will probably strip out before you get enough torque applied to move them. Then you'll need something like http://www.aldn.com/grabit/ then you'll need to replace the screws.
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