KTM LC4 625 SXC Brake Issue

DirtMerchant · 10-08-2007, 08:37 PM

Hey fellows,

I have reviewed and searched LC4 thread(s) but can't find an answer to my problem.

I have recently bought an 03 SXC, it is in great condition with about 1,300 miles on it. The front brake has been pretty soft but will stop the bike. I bought a fresh container of Mutol 5.1 brake fluid and proceeded to bleed the front brake.

I tried using a syringe to push the fluid backwards into the resivor but there was too much pressure and was leaking out around bleeder. I then went about the ole' timey way and pumped about 5 resivors full until I was sure that I had all the old fluid out. I pumped and pumped and pumped and pumped; all to no avail. I could not get it to build pressure.

I turned the bars to the left and then pushed the caliper against the rotor to push fluid back up; no go. I then removed the master cylinder, held it up so there is no bend in the brake line and pumped it about a hundred times whilst thumping it with may palm. This got me back to some pressure but will not build up pressure like it should. Any suggestions??????

I did notice there is a small about of fluid weeping out around the dust cover of the piston on master cylinder; but I did pump the hell out of it.

How long will brake fluid last in the container? I squeezed all the air out of the container and put it in a Ziplock bag.

Thanks,

Rodney

soloyosh · 10-08-2007, 10:28 PM

I bought a second resavoir cap and made an attachment for my pressure bleeder.

Before that I would remove the caliper and hang it from a shelf, above the m/c. Tap the lines a few times to knock the bubble loose and bleed like you would anything else. Just make sure you lower the caliper back down before opening the m/c to top off.

Hipster · 10-09-2007, 04:59 AM

Dirtmerchant,

Check the index, there is a special technique for removing air from the front brake. If I remember correctly, it involves pressing against the caliper with your knee while bleeding the brake.

BobCWNC · 10-09-2007, 09:18 AM

A careful application of a heat gun to strategic places will thin the fluid so that bubbles will float to the high spots easier.

redveloce · 10-09-2007, 09:40 AM

Quote:

Originally Posted by Hipster

Dirtmerchant,

Check the index

I searched the index and wasn’t able to find anything on this. The brakes are very spongy on my ’03 SXC as well. I thought it was just the nature of the braking system for some reason. I’ve tried to bleed the brakes several times with no effect.

DirtMerchant · 10-09-2007, 12:12 PM

Quote:

Originally Posted by Hipster

Dirtmerchant,

Check the index, there is a special technique for removing air from the front brake. If I remember correctly, it involves pressing against the caliper with your knee while bleeding the brake.

Been there, tried that. I pushed against it, thumped it with my palm but no workey.......

The rear brake was a breeze so I know I'm not doing it wrong.

DirtMerchant · 10-09-2007, 12:15 PM

Quote:

Originally Posted by redveloce

I searched the index and wasn’t able to find anything on this. The brakes are very spongy on my ’03 SXC as well. I thought it was just the nature of the braking system for some reason. I’ve tried to bleed the brakes several times with no effect.

CLICK HERE:
http://www.advrider.com/forums/showthread.php?t=102248

Beez · 10-09-2007, 01:37 PM

Does it use the same master cylinder as the RFS KTMs? There is a lot of discussion on KTMtalk on this issue. There are lots of ideas on how to fix it but the most difinitive one is to replace the entire master cylinder assembly with a Nissin MC from a Honda.

One thing you can try is to drill another hole in the MC banjo bolt. So instead of 2 holes at 180˚ you have 4 holes at 90˚. Less chance of a bubble getting trapped there.

Another trick is to tighten a zip-ty around the grip and brake lever and leave it overnight. Turn the bars to the left so the MC is as high as can be. The next day the brakes should feel better. I did this on a 450 EXC once and it worked, I don't know why.

DirtMerchant · 10-09-2007, 04:48 PM

Quote:

Originally Posted by Beez

Does it use the same master cylinder as the RFS KTMs? There is a lot of discussion on KTMtalk on this issue. There are lots of ideas on how to fix it but the most difinitive one is to replace the entire master cylinder assembly with a Nissin MC from a Honda.

One thing you can try is to drill another hole in the MC banjo bolt. So instead of 2 holes at 180? you have 4 holes at 90?. Less chance of a bubble getting trapped there.

Another trick is to tighten a zip-ty around the grip and brake lever and leave it overnight. Turn the bars to the left so the MC is as high as can be. The next day the brakes should feel better. I did this on a 450 EXC once and it worked, I don't know why.

Beez,

Thanks for the input; I am not sure if the MC is the same as RFS or not. I also have been wanting to put a pressure switch for brake light so if I need to swap out for a Nissin then now is the time before dumping more cash into the a switch..........

I will be heading to the shop to try the zip tie trick. I have a centerstand instead of side stand so I am not sure how much turing left will help but I'll try.

Rodney

Gumbydave · 10-09-2007, 05:37 PM

regarding backbleeding the magura
When it happens that the fluid will not backbleed I have found it to be because fluid will not pass between the line and the reserviour through the tiny hole seen in the bottom of the res.
this can happen because the lever is not adjusted all the way back,or dirt holding it open which is not allowing the fluid to pass
or
the green piston cup seal on the master cyl is distorted blocking the hole. It can be confirmed by poking a needle in while backbleeding. It can be cured with a replacement MC piston from ktm

DirtMerchant · 10-09-2007, 05:48 PM

Quote:

Originally Posted by Gumbydave

regarding backbleeding the magura
When it happens that the fluid will not backbleed I have found it to be because fluid will not pass between the line and the reserviour through the tiny hole seen in the bottom of the res.
this can happen because the lever is not adjusted all the way back,or dirt holding it open which is not allowing the fluid to pass
or
the green piston cup seal on the master cyl is distorted blocking the hole. It can be confirmed by poking a needle in while backbleeding. It can be cured with a replacement MC piston from ktm

The MC is a Brembo on this bike, clutch is Magura though.

Bike is sitting for 24 hrs with tiewire around brake lever, bars turned left and block under right side of centerstand.....

Rodney

halfcab · 10-10-2007, 03:26 AM

Did you check to see if your some one had changed from the stock brake pads on your 03 SXC to after market pads?

A lot of people change out the stock pads to after market because some owners think the stock pads are to touché. Are they don't want to pay almost twice the price for stock pads when they replace.

DirtMerchant · 10-10-2007, 06:31 AM

Quote:

Originally Posted by halfcab

Did you check to see if your some one had changed from the stock brake pads on your 03 SXC to after market pads?

A lot of people change out the stock pads to after market because some owners think the stock pads are to touché. Are they don't want to pay almost twice the price for stock pads when they replace.

The problem I am experiancing is the front brake lever is way to soft; as if there is a bunch of air in the lines but can't get it to purge. Maybe I need to put a Viagra in the MC reservoir.

The guy I bought it from said he had not serviced the brakes so I am assuming they are stock. I didn't remove the pads but they don't look too worn.

Rodney

DirtMerchant · 10-10-2007, 06:10 PM

Quote:

Originally Posted by Beez

Another trick is to tighten a zip-ty around the grip and brake lever and leave it overnight. Turn the bars to the left so the MC is as high as can be. The next day the brakes should feel better. I did this on a 450 EXC once and it worked, I don't know why.

You sir, are a frigging genius but now I need to start a new thread to address my new problem. Front Brake Overly Sensitive; will nearly throw me over the bars with one fingers pressure.

I ordered a front brakelight pressure switch/banjo bolt so I guess I will be trying my luck again in a week or two.

THANKS TO EVERYONE FOR YOUR INPUT

Rodney

Beez · 10-11-2007, 07:32 AM

Quote:

Originally Posted by DirtMerchant

You sir, are a frigging genius

10-08-2007, 08:37 PM	#1
DirtMerchant ^OP Beastly Adventurer Joined: Aug 2004 Location: Florida Oddometer: 1,460	KTM LC4 625 SXC Brake Issue Hey fellows, I have reviewed and searched LC4 thread(s) but can't find an answer to my problem. I have recently bought an 03 SXC, it is in great condition with about 1,300 miles on it. The front brake has been pretty soft but will stop the bike. I bought a fresh container of Mutol 5.1 brake fluid and proceeded to bleed the front brake. I tried using a syringe to push the fluid backwards into the resivor but there was too much pressure and was leaking out around bleeder. I then went about the ole' timey way and pumped about 5 resivors full until I was sure that I had all the old fluid out. I pumped and pumped and pumped and pumped; all to no avail. I could not get it to build pressure. I turned the bars to the left and then pushed the caliper against the rotor to push fluid back up; no go. I then removed the master cylinder, held it up so there is no bend in the brake line and pumped it about a hundred times whilst thumping it with may palm. This got me back to some pressure but will not build up pressure like it should. Any suggestions?????? I did notice there is a small about of fluid weeping out around the dust cover of the piston on master cylinder; but I did pump the hell out of it. How long will brake fluid last in the container? I squeezed all the air out of the container and put it in a Ziplock bag. Thanks, Rodney

10-08-2007, 10:28 PM	#2
soloyosh Dad and husband Joined: Nov 2004 Location: LHC, AZ Oddometer: 5,465	I bought a second resavoir cap and made an attachment for my pressure bleeder. Before that I would remove the caliper and hang it from a shelf, above the m/c. Tap the lines a few times to knock the bubble loose and bleed like you would anything else. Just make sure you lower the caliper back down before opening the m/c to top off. __________________ 2007 Aprilia RXV 5.5

10-09-2007, 09:18 AM	#4
BobCWNC Orange lithotripter Joined: Mar 2006 Location: Freakin AVL Oddometer: 13,041	A careful application of a heat gun to strategic places will thin the fluid so that bubbles will float to the high spots easier. __________________ __________ "It is a great art to saunter". Thoreau “Life’s most persistent and urgent question is– what are you doing for others?” –Martin Luther King, Jr. Alan Greenspan said out loud, “I have found a flaw.” Waxman pushed him, responding, “In other words, you found that your view of the world, your ideology, was not right; it was not working.” “Absolutely, precisely,” Greenspan said

10-09-2007, 05:37 PM	#10
Gumbydave motorcycle doofus Joined: Jan 2006 Location: So.California Oddometer: 884	regarding backbleeding the magura When it happens that the fluid will not backbleed I have found it to be because fluid will not pass between the line and the reserviour through the tiny hole seen in the bottom of the res. this can happen because the lever is not adjusted all the way back,or dirt holding it open which is not allowing the fluid to pass or the green piston cup seal on the master cyl is distorted blocking the hole. It can be confirmed by poking a needle in while backbleeding. It can be cured with a replacement MC piston from ktm __________________ "wise proverb witheld pending further review" 04 950 rat bike 06 KTM 576 XC/E-adv 06 KTM 250 XCW TrailTricks Suspension

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10-09-2007, 04:59 AM	#3
Hipster Beastly Adventurer Joined: Aug 2004 Location: Mpls, Mn. Oddometer: 1,433	Dirtmerchant, Check the index, there is a special technique for removing air from the front brake. If I remember correctly, it involves pressing against the caliper with your knee while bleeding the brake.

10-09-2007, 01:37 PM	#8
Beez Given to fly Joined: Aug 2004 Location: Framingham, MA Oddometer: 5,498	Does it use the same master cylinder as the RFS KTMs? There is a lot of discussion on KTMtalk on this issue. There are lots of ideas on how to fix it but the most difinitive one is to replace the entire master cylinder assembly with a Nissin MC from a Honda. One thing you can try is to drill another hole in the MC banjo bolt. So instead of 2 holes at 180˚ you have 4 holes at 90˚. Less chance of a bubble getting trapped there. Another trick is to tighten a zip-ty around the grip and brake lever and leave it overnight. Turn the bars to the left so the MC is as high as can be. The next day the brakes should feel better. I did this on a 450 EXC once and it worked, I don't know why.

10-10-2007, 03:26 AM	#12
halfcab Studly Adventurer Joined: Apr 2007 Location: Dog Patch S.C. Oddometer: 645	Did you check to see if your some one had changed from the stock brake pads on your 03 SXC to after market pads? A lot of people change out the stock pads to after market because some owners think the stock pads are to touché. Are they don't want to pay almost twice the price for stock pads when they replace.