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Hello my 2013 ktm 300xc front brake is losing pressure. When I pull in the lever, you have to pump it a couple times to build pressure. I can hold it in and It won't lose pressure, but when I let it off and ride a little I have to repeat the process. All I've done is bleed the brake and top off to get rid of a sponge feel. That diddnt even solve the spongeyness lol. The master shouldn't need a rebuild, it was working just fine before. Thanks.
 

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fix it like it was before you fixed it

make sure you have a free clearance at the actuator pin. adjust for 2-3mm clearance. remove master cylinder cover and wrap a rag around master to catch dripping fluid. take a screwdriver and compress caliper pistons back into their bore with screwdriver prying brake pad back. the reversal of fluid should purge air or aerated fluid through master cylinder. pump brake lever a few times to reset caliper clearance and top up fluid and see if that wont help you. good luck
 

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KTM's front brake and me we are not friends!

Ever since we started riding 85's we replace the front brake master cylinder with a Yamaha one. It is the same Yamaha one, I just move it to our racing bike everytime we get a new bike. We have now had that Yamaha one for 6 years and never rebuilt it. We fit the thing and forget it. (And it was an old s/h one I got cheap). I take it from one bike, fit it to the next one, fill it with brake fluid, pump untill it works and that is it. no bleeding nothing. Just keeps on working and never any sponge feel. Those KTM ones on the other hand... I rebuild them, spend hours bleeding them, tapping the hose, reverse bleeding +more and I get them right. Then 2 - 3 race meetings later "Dad, the front brake is not working..." I hate being beaten by mechanical things, but to spend hours every month trying to fix a KTM front brake... nope, never again. I have no idea how many rebuild kits I have fitted to the KTM ones. I have tried different suppliers and kits. No go.
 

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Discussion Starter #6
Ever since we started riding 85's we replace the front brake master cylinder with a Yamaha one. It is the same Yamaha one, I just move it to our racing bike everytime we get a new bike. We have now had that Yamaha one for 6 years and never rebuilt it. We fit the thing and forget it. (And it was an old s/h one I got cheap). I take it from one bike, fit it to the next one, fill it with brake fluid, pump untill it works and that is it. no bleeding nothing. Just keeps on working and never any sponge feel. Those KTM ones on the other hand... I rebuild them, spend hours bleeding them, tapping the hose, reverse bleeding +more and I get them right. Then 2 - 3 race meetings later "Dad, the front brake is not working..." I hate being beaten by mechanical things, but to spend hours every month trying to fix a KTM front brake... nope, never again. I have no idea how many rebuild kits I have fitted to the KTM ones. I have tried different suppliers and kits. No go.

Great idea I will certainly be there when I need to rebuild it.
 

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Discussion Starter #7
make sure you have a free clearance at the actuator pin. adjust for 2-3mm clearance. remove master cylinder cover and wrap a rag around master to catch dripping fluid. take a screwdriver and compress caliper pistons back into their bore with screwdriver prying brake pad back. the reversal of fluid should purge air or aerated fluid through master cylinder. pump brake lever a few times to reset caliper clearance and top up fluid and see if that wont help you. good luck
I will try this thank you!
 

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Discussion Starter #8
make sure you have a free clearance at the actuator pin. adjust for 2-3mm clearance. remove master cylinder cover and wrap a rag around master to catch dripping fluid. take a screwdriver and compress caliper pistons back into their bore with screwdriver prying brake pad back. the reversal of fluid should purge air or aerated fluid through master cylinder. pump brake lever a few times to reset caliper clearance and top up fluid and see if that wont help you. good luck
Hey augiedoggie I tried compressing the caliper and pumping a couple times. It did give a better feel when it has pressure but it did not help the problem. I did notice that the top piston comes out first. Once that one compresses, the other follows. I did notice that the loss of pressure only happens when I am moving I think.
 

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Give him a brake??

I wonder if your observation of caliper movement could indicate a stuck piston. One stuck piston can cause your symptom. You have to be careful when testing because the piston can be forced from caliper when not restrained by pads and rotor. Once you compress pistons you will need to pump brake to return pads to rotor surface and restore lever feel. It could be possible the slow moving caliper piston requires this additional lever pumping to move it. You can test for stuck piston by removing caliper and pads and restraining your good piston with C clamp or vice grip and compress brake lever several times. Your piston should move outward with each pump of lever and not retract. Careful to only pump a few times or piston can exit caliper and cause a new set of problems. You can retract caliper pistons with C clamp on both pistons at the same time. Or put pad or block across caliper pistons to prevent pistons from blowing out of caliper.
 

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Discussion Starter #10
I wonder if your observation of caliper movement could indicate a stuck piston. One stuck piston can cause your symptom. You have to be careful when testing because the piston can be forced from caliper when not restrained by pads and rotor. Once you compress pistons you will need to pump brake to return pads to rotor surface and restore lever feel. It could be possible the slow moving caliper piston requires this additional lever pumping to move it. You can test for stuck piston by removing caliper and pads and restraining your good piston with C clamp or vice grip and compress brake lever several times. Your piston should move outward with each pump of lever and not retract. Careful to only pump a few times or piston can exit caliper and cause a new set of problems. You can retract caliper pistons with C clamp on both pistons at the same time. Or put pad or block across caliper pistons to prevent pistons from blowing out of caliper.
Good thinking I will try this. But I wonder how this could arise from bleeding the brakes. I did hook up a syringe in an effort to push fluid up the line because I am aware of the pockets of air that form at the top. When that diddnt work I bleed them by cracking the bleeder until they worked.
 

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Keep pumping

I have had some miserable front brake problems and some require crazy tactics. Full disclosure... I usually create these problems myself:frown2:You can hang caliper from shop ceiling with wire to allow air to travel to bleeder. I would hope your trouble can be resolved by reverse bleeding as suggested and making sure master cylinder plunger actuator has proper free play. I suspect you may have a bit of aerated fluid causing the trouble here. Keep at it and good luck. Check back as needed
 

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Discussion Starter #12
I have had some miserable front brake problems and some require crazy tactics. Full disclosure... I usually create these problems myself/images/KTMforums_2015/smilies/tango_face_sad.pngYou can hang caliper from shop ceiling with wire to allow air to travel to bleeder. I would hope your trouble can be resolved by reverse bleeding as suggested and making sure master cylinder plunger actuator has proper free play. I suspect you may have a bit of aerated fluid causing the trouble here. Keep at it and good luck. Check back as needed
Thank you I will play with it some more then just ride it and hopefully it will resolve itself.
 

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Hey guys I found the problem the hard way. While checking over my bike before a race, I discovered my front wheel bearings were shot. One side was clapped enough but the others bearings fell out of the bearing race. Since the wheel had play, believe it or not the brake rotor was pushing the caliper pistons in. Who would of guessed? Thanks for all the help!
 

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Hey guys I found the problem the hard way. While checking over my bike before a race, I discovered my front wheel bearings were shot. One side was clapped enough but the others bearings fell out of the bearing race. Since the wheel had play, believe it or not the brake rotor was pushing the caliper pistons in. Who would of guessed? Thanks for all the help!
You get 10/10 for your honesty! But 4/10 for your bike maintenance... :wink2:
 

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KTM's front brake and me we are not friends!

Ever since we started riding 85's we replace the front brake master cylinder with a Yamaha one. It is the same Yamaha one, I just move it to our racing bike everytime we get a new bike. We have now had that Yamaha one for 6 years and never rebuilt it. We fit the thing and forget it. (And it was an old s/h one I got cheap). I take it from one bike, fit it to the next one, fill it with brake fluid, pump untill it works and that is it. no bleeding nothing. Just keeps on working and never any sponge feel. Those KTM ones on the other hand... I rebuild them, spend hours bleeding them, tapping the hose, reverse bleeding +more and I get them right. Then 2 - 3 race meetings later "Dad, the front brake is not working..." I hate being beaten by mechanical things, but to spend hours every month trying to fix a KTM front brake... nope, never again. I have no idea how many rebuild kits I have fitted to the KTM ones. I have tried different suppliers and kits. No go.
hey Axzon what Yamaha master cylinder did you swap to? I’m looking to find out if it would be suitable for my 2013 350 free ride as I’m sick of having no pressure on the brake lever
 

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Message sent. And yes, I am sure it will work on the Freeride!
 

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Hello my 2013 ktm 300xc front brake is losing pressure. When I pull in the lever, you have to pump it a couple times to build pressure. I can hold it in and It won't lose pressure, but when I let it off and ride a little I have to repeat the process. All I've done is bleed the brake and top off to get rid of a sponge feel. That diddnt even solve the spongeyness lol. The master shouldn't need a rebuild, it was working just fine before. Thanks.
For me it turned out to be a slight warp of the brake rotor. Riding would expand the brake pads for the apparent "fat" rotor. Pumping the brakes would return the pads back to normal position and make them "work" again until you release the lever. In the "No Brake" situation, put the bike on a stand, front, or back wheel free spinning. Spin the wheel and pump the brake once, see if you have a slight drag during only part of the rotation of the wheel.
 
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