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Discussion Starter · #1 ·
I replaced the front brake pads and put another master cylinder on my bike. I bleed the master cylinder 1st by pumping the brake lever several times and held it then loosened and tightened the banjo bolt. It seems like i got all the air out of the master cylinder because there are no air bubbles coming up in it when i pump the brake lever...

Then i pumped the brake lever and held it then loosend and tightened the caliper bleeder valve and did this quite a few times and made sure that the fluid level in the master cylinder didn't get low. I put a loop in the drain hose that i used and filled the drain cup with fluid to make sure no air got in that way...

The brakes still feel spongy...you have to pull the brake lever in almost half way before the brake lever gets hard. I'm wondering how many times you might have to bleed it at the caliper to get all of the air out of the brake line?
 

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I was having the same problem so I pulled the cover off the MC reservoir. With the front wheel cocked all the way to the left (elevating the piston end of the MC) and tapping on the MC with a screwdriver handle, some air bubbles came up out of the piston bore through the plastic disc in the bottom of the reservoir. I would guess you could remove the MC from the handlebar and slowly tip it back and forth while tapping on it to release any bubbles. It doesn't take much air in the system to get that spongy feel.
 

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Patriot Guardian
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The loop in the hose and filling the drain cup won't help if you release the lever before closing the bleed valve... the MC's piston travel is not enough to completely clear the tubing.

Pick up a "Mighty-Vac"... works wonders. You connect it to the bleeder valve and draw a vacuum on it, then open the valve and pull the lever. The vac will draw fluid through the system and quickly drain the master cylinder, so have a refill bottle handy.
 

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Discussion Starter · #4 ·
i closed the bleed valve before i released the brake lever...i'm sure the vacuum brake bleeders are nice and save a lot of time i'll keep my eye out for one on ebay.

i'll try awhtx's advice with the master cylinder. I bleed the brakes with the wheel centered i did tap on the brake line several times with a screwdriver but not the MC...i'll keep working with it and see if it gets any better
 

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Tree Magnet
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Bungee cord or zip tie the brake cable to the grip overnight. Tap the line every once in a while like you have been. If you were taking a road trip, I'd say throw the bike in the truck. Keeping the lever squeezed should allow the bubbles to work their way to the surface.
 

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Tree Magnet
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Works well for my buddies on KTMs with their notoriously spongy front brake. The keep it bungeed on the way to the race, and the vibration sends all the air bubbles to the top! Imagine that - a good idea from a punmpkinhead.
 

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Slow Guy on a Fast Bike
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You don't say what year your working on, Kawis have long been known for spongy brakes. A stainless steel line will help, but if there is wear in the pin area you may not get the feel you want. I use a syringe with a piece of tubing, then attach to the bleeder, open it up and pull on the syringe (keeping an eye on the master cylinder fluid level) once you stop getting air you can close the bleeder and pump up the brakes then hold the lever and release out of the bleeder. Once the air is out leave it and come back tomorrow and repeat the process. As an FYI the newer master cylinders are much better than the old ones and will work on bikes back to the 90's and can be picked up off Ebay for cheap.
 

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Discussion Starter · #10 ·
it's a 93 kx125...i have something like a syringe i'll try that out too. Yeah, i have noticed that the newer model bikes have much better brakes than the older ones.

When i've gone to the kawa shop i've tested the brakes on the new bikes and they have a much better feel and i'm sure they stop you a lot better too...
 

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Luv my big boy toys
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I replaced the front brake pads and put another master cylinder on my bike. I bleed the master cylinder 1st by pumping the brake lever several times and held it then loosened and tightened the banjo bolt. It seems like i got all the air out of the master cylinder because there are no air bubbles coming up in it when i pump the brake lever...

Then i pumped the brake lever and held it then loosend and tightened the caliper bleeder valve and did this quite a few times and made sure that the fluid level in the master cylinder didn't get low. I put a loop in the drain hose that i used and filled the drain cup with fluid to make sure no air got in that way...

The brakes still feel spongy...you have to pull the brake lever in almost half way before the brake lever gets hard. I'm wondering how many times you might have to bleed it at the caliper to get all of the air out of the brake line?
You don't bleed any brakes via the banjo bolt, you'll never get all of the air out. Use the bleeders, that's what they're for.
Squeeze the brake, then crack (open) the bleeder & close it quickly then release the brake, repeat as necessary. Do not release the brake with the bleeder open, it will suck air in.
I prefer to use Valvoline SynPower DOT 4 synthetic brake fluid in all my vehicles (change every 12-24 months) except my truck, that uses air & some alcohol.
 

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Luv my big boy toys
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i closed the bleed valve before i released the brake lever...i'm sure the vacuum brake bleeders are nice and save a lot of time i'll keep my eye out for one on ebay.

i'll try awhtx's advice with the master cylinder. I bleed the brakes with the wheel centered i did tap on the brake line several times with a screwdriver but not the MC...i'll keep working with it and see if it gets any better
The vacuum bleeders are around $20 in a parts store. You might want to check these out too.

Speedbleeders

 

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Discussion Starter · #13 ·
You don't bleed any brakes via the banjo bolt, you'll never get all of the air out.
From what i've read thats how you bleed the master cylinder...hold the brake lever loosen the banjo bolt let the air out tighten bolt release brake lever. If you change the MC or if the fluid gets low you need to bleed from both ends. I tried bleeding from only the caliper 1st and didn't have any brakes at all until i bleed the MC...
 

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Mark in Houston
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Heck I tried it the old fashioned way and got no improvement in my grab. I ran a line from the bleeder valve to a jar of brake fluid and let it drain. Then I pumped the MC 50 times, refilling the MC reservoir all along. Are you saying the MC doesn't move enough stuff to bleed the system this way?
 

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Patriot Guardian
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Heck I tried it the old fashioned way and got no improvement in my grab. I ran a line from the bleeder valve to a jar of brake fluid and let it drain. Then I pumped the MC 50 times, refilling the MC reservoir all along. Are you saying the MC doesn't move enough stuff to bleed the system this way?
Did you release the lever with the bleeder valve still open? If so, you drew fluid (and air) right back into the line.

You need to press the lever slightly, open the bleeder, allow the lever to bottom out, close the bleeder, THEN release the lever.

That's what makes Speed Bleeders so nice... they close themselves when you release the lever so you don't have to do the back and forth thing, just pump the lever while refilling the MC.
 

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Mark in Houston
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Hmmm...I thought that sealing a tube from the bleeder to a jar of fluid, would keep air from coming back in on the lever release. Is it that the bubbles are moving up and down with the level pumping?
 

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Patriot Guardian
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Ya, you need to completely force fluid through the system. If you had an air bubble up near the banjo bolt, all you did was move it up and down about 6-8 inches.
 

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Here's a little advice that will always work on a bike if your just trying to get the last little bubbles out.

Like someone said, turn the wheel to the left, try to get it to lean a little to the left as well, but defininately not to the right. If it's flat on a stand, that's ok but better if on the triangle stand. Fill the m/c, and work the lever just slightly and quickly. Just enough to feel a little pressure. Don't make any full pumps. As your doing this, use an item such as a screwdriver handle to tap the line where the bend is coming up over to the m/c. You will see alot of little tiny bubbles start to work their way out.

This is only if the system isn't pressure bled or bench bled to fill everything. Try it.

If it still gets air or feels like it gets worse, you may need a rebuild kit or possibly a new m/c. kits are cheap and easy to do. If you need a new one it's because many times a rider will go down on the right side and it jams the piston in and it scores the wall. Thus the rubber cup seal can't seal and it sucks air. Be aware these seals wear out quickly so you might wanna get a kit and throw some new seals in there.

Sapper
 

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Mark in Houston
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Tx a bunch. I did drop it on the right side a couple weeks ago and the brake lever was one of the things that took the punch
 

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Mark in Houston
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Well, color me stupid. I ordered the speed bleeders...neat gizmos. But my problem was my brake lever was hitting my throttle cable and making it feel bottomed out.,
 
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