Spongy front brake - Kawasaki KLR 650 Forum
2008+ KLR650 Wrenching & Mod Questions For repair, maintaining or modifying discussions related to the newly updated 2008 and beyond, Generation 2 KLR650 Motorcycle.

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post #1 of 16 Old 02-14-2020, 09:09 PM Thread Starter
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Join Date: Oct 2019
Location: Vancouver Island BC
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Spongy front brake

Okay, I'm about at my wits end: 2008, high mileage blah blah blah.
*I've replace the pads, lubed the calipers real nice and slick,
*New master cylinder rebuild kit including a new diaphragm.
*Stainless brake line.
*I've bled the system about a thousand times, both manual and with my Mighty-vac pump according to all the instructions.
*Clamped the lever overnight to 'burp' the system.

Brake lever still comes down to almost touching the grip.
It will stop me, but was much firmer before doing all this.

What have I missed?
Why won't they firm up????????
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post #2 of 16 Old 02-15-2020, 10:17 AM
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Sounds to me as if there is an air bubble up high in the system.

With the reservoir about half full & the cap installed and the front wheel turned Left, compress the caliper piston back into the caliper bore.
This will many times purge an air bubble out of the upper banjo bolt & master cylinder bore back into the reservoir. Slowly, smoothly pump up the handlever and repeat.
DPelletier and Weav like this.

pdwestman
Modify at "YOUR OWN RISK"!

Still riding my 1987 KL650-A1. 85,000+ miles & counting
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post #3 of 16 Old 02-16-2020, 08:06 PM Thread Starter
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Thanks for the suggestion pdwestman.
Tried it, but same thing. Still soft.
: (

No leaks anywhere.
As much as I hate to, I think I'm going to have to take it in to a mechanic unless anyone else has any suggestions?

Last edited by Eldubya; 02-17-2020 at 09:46 AM.
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post #4 of 16 Old 02-17-2020, 05:05 PM
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Join Date: Nov 2015
Location: Champaign, IL USA
Posts: 48
So...

-get a bunch of wet towels to place on painted body parts beneath, to the side, to the front... wherever you figure brake fluid might spray or drip in the area of the banjo bolt on the master cyl. Wear safety glasses and crappy clothes,

-have a spray bottle full of water close by,

-crack the banjo bolt slightly,

-loosen the banjo bolt slowly while squeezing the brake lever,

-watch for fluid and hopefully a burp of air.

Do this a couple of times. Tighten the banjo bolt properly, spray water on any areas you even think have brake fluid on them.

Make sure your reservoir is full, and good luck.
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post #5 of 16 Old 02-17-2020, 07:53 PM Thread Starter
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Thanks ymracing.
Did as you suggested, no luck. In fact now they have zero resistance and I can't build up any pressure.
Grrrr!
: /
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post #6 of 16 Old 02-17-2020, 08:57 PM
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Are you sure that there is much fluid in the system at all? If you open the bleed screw and push the lever do you get a stream of fluid free of any bubbles out?

If you do, and you are bleeding the system, can you empty the reservoir with a dozen pumps or so?

Sound like you have air in the actual pressure cylinder inside the reservoir housing.
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post #7 of 16 Old 02-18-2020, 04:15 PM
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Quote:
Originally Posted by Eldubya View Post
Thanks ymracing.
Did as you suggested, no luck. In fact now they have zero resistance and I can't build up any pressure.
Grrrr!
: /
Did you replace all the washers in your banjos, they are one use only. Are all of your banjo bolts correctly torqued, and your bleed screw in good condition? O2 molecules are sneaky!

So, now it's time to disconnect the brake line from the m/c (master cylinder) and the caliper. Drain it first!

-Push the brake pistons back as far as you can. I use a "C" clamp and the pads.

***DO NOT LET THE M/C BECOME LOW ANYTIME DURING THIS PROCEDURE***

-Bench prime the m/c.

-Attach the top of the brake line, with new washers, torqued properly, to the m/c.

-Place the caliper end of the hose in a catch can for the brake fluid you're going to lose.

-Pour brake fluid into the m/c until you have a continuous stream.

-Finger and thumb over banjo holes, top off the m/c.

-Pull in the brake lever slowly. If you feel fluid pressure on your finger/thumb, and you should...great. If not buy another gallon of brake fluid and repeat.

-Attach your brake line to the caliper, with new washers!

-Snug the banjo bolt very lightly.

-Wet rags and H20 spray bottle on hand, pull in the brake lever slowly. You should have bubbles and brake fluid leaking around the banjo bolt and "new washers". If not loosen a smidge.

-Hold brake lever tightly to the handle and tighten the banjo bolt.

-Let go of the brake lever.

-Open the caliper bleed screw totally.

-Start putting brake fluid into the m/c until it flows out of the caliper bleed screw.

-When you have a nice flow of fluid from the bleed screw, close it.

-Now..you may start "bleeding" the brakes.

Hoping this will get you going...and stopping!
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post #8 of 16 Old 02-20-2020, 03:58 AM
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Use a vacuum pump

I am a mechanic and have had his issue with many bikes often resorting to bleeding the banjo bolt at master cylinder but best results come from using a vacuum pump to bleed the brakes. If you have not used a vacuum pump, they are relatively cheap and easy to use.
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post #9 of 16 Old 02-20-2020, 11:22 AM
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Eldubya, is it possible that your master cylinder rebuild kit or quality of labor was not up to par?

pdwestman
Modify at "YOUR OWN RISK"!

Still riding my 1987 KL650-A1. 85,000+ miles & counting
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post #10 of 16 Old 02-20-2020, 04:00 PM
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Quote:
Originally Posted by pdwestman View Post
Eldubya, is it possible that your master cylinder rebuild kit or quality of labor was not up to par?
Yes, I was thinking the same thing. Something in the master cylinder may be incorrectly assembled.

Jason
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