2013 KTM 250 SX Brake Issues

Edited Date/Time 5/15/2014 5:45pm
So I just took the bike for a quick ride on this little turn track near the house.

About five minutes in the rear brake completely went away; no pedal. Didn't see any fluid leaking or anything damaged, but I still wanted to ride so I said I would figure it out when I got home.

Couple minutes later the front brake completed locked up. I could feel the lever getting pretty stiff and when I stopped to check it out, the wheel was locked up. Again nothing looked damaged and I had to push the bike 1/4 mile back to my truck with a locked up front wheel...talk about a work out. Anyway, by the time I got out of my gear and was ready to push the bike up my ramp into the truck, the front wheel was no longer locked up. Still had no rear brake.

Could I have heated the front brake up that much to the point of it locked up the front wheel? I wasn't riding hard at all, mainly in first gear hitting a couple turns nice and easy. Since I was already out of my gear and it was getting late, I didn't ride the bike again. Honestly, I'm not sure if everything is fine. I'm afraid if it happens again and I'm hauling around a track, I'll get sent over the bars and it won't end well.

Any thoughts?

Thanks.
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5/11/2014 5:04pm
Have you over filled the brake reservoirs? When the fluid gets hot it expands. If left with no place to go it can only push the pistons out.

Otherwise check all the sliding pins for corrosion and straightness. And if those were good I would pull the pistons from the caliper any give them an inspection. And fresh brake fluid for sure.

Brakes are a safety item so if you are unsure about anything let someone qualified handle it.
Markee
Posts
3661
Joined
4/15/2013
Location
Suffolk, VA, USA
5/12/2014 1:13pm
Very strange. Your brake system is a closed loop system and a hydraulic one at that. If you push/pull your lever and nothing happens, that energy is going somewhere, and the fact that you have one of the best braking systems on a production bike sends a red flag.

Keep it simple... Bleed your brakes, inspect your wear items and like fulltime said, check your pins for corrosion.
5/13/2014 1:42pm
Happend to me last race season, it was a bummer.
Use DOT 5.1 as it has a higher boiling point, and make sure that you "flushed the system with the new fluid. Mine ended up warping the little rubber seal on the dust cover and had to buy a "rebuild kit" from KTM usually around $40.

The Shop

GRIFF
Posts
6
Joined
8/15/2006
Location
Poplar Bluff, MO, USA
5/13/2014 6:12pm
You need to get a rebuild kit from your dealer. When I was a KTM dealer we had this quite a bit.
hellion
Posts
1089
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12/19/2009
Location
Westfield, MA, USA
5/15/2014 6:57am
The front brake problem sounds like too much fluid. The rear brake problem is a problem that's common to me. I'm a brake dragger and can't break the habit, and I always lose my rear brakes when riding my turn track. Given time to cool down they always come back, but the fluid is then toasted so I flush the system with fresh fluid. The components are designed to be light weight and they just can't absorb that much heat. On the older models it was common to wear or tear the seal in the master cylinder but that seems to be rectified on the newer models. BTW, I've tried all the expensive brake fluids and for me none of them worked well enough to stop the problem.
5/15/2014 5:08pm
Hey, just wanted to give you an update. I definitely think the fluid was a little high, may have been the problem. I was using Motorex 5.1 and stuck with the same stuff, just fresh fluid. Greased up the pin on the caliper and checked the pistons and, from what I can tell, they looked good.

One question, as you push in one one piston, the other piston should move outward correct? Basically, as one piston moves in, the others moves out and vice versa. I'm guessing that ensures even pressure on the pads and disc?

Thanks again

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