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Discussion Starter · #1 ·
Hello and thanks in advance for helping this new KLR owner with a front brake issue. New to motorcycles, new to this forum.
My 2009 KLR front brake will randomly start to drag and after a few minutes of dragging, it get worse and worse, to the point where I need to pull over and the front brake feels fully engaged. When I open the bleeder screw a little bit of brake fluid shoots out, then the brake goes back to normal. I have driven 100 miles and it's not done it, but on my 3 mile commute to work it happens...at random.

I already flushed the system with new DOT 4 brake fluid, took off the caliper, inspected the pins, slides, and pistons. Hit all of those parts with some brake cleaner and a brush, lubed, and put back together.

When this starts to happen the brake lever gets SUPER stiff, like I can barely pull it. This makes me think it's a hydraulic issue, not a caliper issue. Could the master cylinder need a rebuild? Is there any return port on the MC that may be clogged? Any advice is much appreciated!

Thanks,
Erich
 

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Erich,
There are 2 ports in the floor of the front brake reservoir. The one closest to the brake hose is about the size of a red human hair or maybe 4 lb monofilament fishing line. The brake piston needs to pull back behind it, to relief internal pressure.
There is an adjustment screw and lock nut on the Gen 2 F. Brake Lever, try loosening the nut and back the screw Out until you have a little clearance between screw tip and brake cylinder piston.
 

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Discussion Starter · #3 ·
Erich,
There are 2 ports in the floor of the front brake reservoir. The one closest to the brake hose is about the size of a red human hair or maybe 4 lb monofilament fishing line. The brake piston needs to pull back behind it, to relief internal pressure.
There is an adjustment screw and lock nut on the Gen 2 F. Brake Lever, try loosening the nut and back the screw Out until you have a little clearance between screw tip and brake cylinder piston.
The adjustment screw on the lever is all the way in but there is still a small gap b/w the screw and the MC plunger.
The small port you refer to is the return port, correct? Should I put a pin in there to make sure there isn't any crud built up? Can I do that without removing the plunger and taking the MC apart?
 

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No, I don't suggest using just any pin.
A tapered broach for cleaning natural gas or propane gas jets is smaller/better.

The return port will usually create a 'fountain' if one squeezes the brake lever with the cover and diaphragm removed. Brake fluid will damage paint. I recommend a giant plastic garbage bag be deployed and taped into/onto position to protect your bike.
If you don't get a fountain, suck out or bleed out the excess fluid, then use the broach to clean the hole.
Put the cap cross-wise across the hole and compress the wheel cylinder to expel crude up into reservoir, suck the crude out with turkey baster or medical pipet. Partially re-fill the reservoir and try again.
 

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Discussion Starter · #5 ·
No, I don't suggest using just any pin.
A tapered broach for cleaning natural gas or propane gas jets is smaller/better.

The return port will usually create a 'fountain' if one squeezes the brake lever with the cover and diaphragm removed. Brake fluid will damage paint. I recommend a giant plastic garbage bag be deployed and taped into/onto position to protect your bike.
If you don't get a fountain, suck out or bleed out the excess fluid, then use the broach to clean the hole.
Put the cap cross-wise across the hole and compress the wheel cylinder to expel crude up into reservoir, suck the crude out with turkey baster or medical pipet. Partially re-fill the reservoir and try again.
Thanks I'll give this a try tomorrow. Does the fountain action happen the pull of the lever or when the lever is released? I do recall some geyser-type action in the reservoir when I was bleeding the brakes but don't recall in which direction.
 

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Discussion Starter · #6 ·
Erich,
There are 2 ports in the floor of the front brake reservoir. The one closest to the brake hose is about the size of a red human hair or maybe 4 lb monofilament fishing line. The brake piston needs to pull back behind it, to relief internal pressure.
There is an adjustment screw and lock nut on the Gen 2 F. Brake Lever, try loosening the nut and back the screw Out until you have a little clearance between screw tip and brake cylinder piston.
Took apart my master cylinder today, replaced the plunger and gaskets, and replaced the front brake line with a steel braided one. So far the bike seems to be riding great, with no brake stick. I will follow up in a few days to make sure this was a fix to my issue for future readers.
To clarify, there is only one port/hole inside the MC housing. I assume this port is used for both outflow and inflow/return. There is not a second port to be cleaned with a wire or otherwise. I am pretty sure my issue was with the MC plunger and gaskets. The plunger was covered in some dried up crud, maybe old grease, not sure. Seems to be working fine now.
 

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Glad to hear you've got your front brake operating properly.

I just removed the reservoir cap from my brothers '09 Gen 2. Unlike the Gen 1 master cylinder, the Gen 2 model has about a 1/2inch "anti-fountain" rubber disc covering the 2 ports, like the KX dirt bikes have had for years. Can't see the two holes.
 
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