ASK THE MXPERTS: MY HUSKY REAR BRAKE WENT OUT
The rear brake on my 2021 Husqvarna FC250 went out suddenly at the track. Luckily, I lost my rear brake on a safe part of the track and easily used the front brake to pull off the track. But, I couldn’t figure out what went wrong with my bike’s brake. I checked the brake fluid and it was okay. I checked the brake pads for fluid on them, but they were dry. I checked the master cylinder pull rod to make sure that it had not gotten too much free play in it. Everything was fine, so I topped off the rear master cylinder and went for a test ride. No brakes! Where should I look next?
You should look behind the rear brake’s master cylinder. That is where the KTM brake line comes out of the master cylinder and loops back to the rear brake caliper. We don’t exactly know how it happens, but sometimes the looping brake line touches the exhaust pipe in the tight confines of this area. If the brake line touches the exhaust pipe, it will melt. If KTM had spec’ed the typical rear brake hose, the pipe would burn a big hole in the brake line instantly and brake fluid would spew all over your bike’s swingarm. Fortunately, KTM uses braided steel brake hoses, which slow the heat from melting the hose and creating a big hole, but eventually, the exhaust pipe’s heat will melt the braided steel wire encasing the actual brake hose. The braided steel slows down the melting process to the point where the pipe can only melt a small hole between the wire braids. That small hole will still be big enough to allow your brakes to lose hydraulic pressure and fail, but not big enough to create a big oily mess that would be an obvious clue as to what went wrong.
The solution to this problem is to get down on your hands and knees and take a close look at your bike’s rear brake hose loop. It should not be touching your exhaust pipe. If it is very close to the pipe, loosen the line’s fitting and rotate the hose clockwise to move it closer to the frame. If you run an aftermarket pipe, be sure to check the clearance before your first ride.