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Rear brake locked up!! Please help!!


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I have a 2011 xcf 250 and haven't had any troubles. We took a little break from riding then as we got back on the bikes I went to use my rear brake and the pedal was stiff. I slammed it down and it un-stiffened So I thought it was fine. Next corner I barely touch the pedal and it locked the rear tire and got stuck down. I had to kick the lever back up and then it worked fine the rest of the day. Why would this of happened?

Edited by ParkerM85
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Caliper gets hot from long down hill or dragging the brakes while riding. Fluid heats up and expands and applys the brake, old fluid with water does it worse.  May have also had a rock or stick holding the pedal.  Trail fix is to dribble water on the caliper to cool it off.

Edited by highmarker
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15 minutes ago, highmarker said:

Caliper gets hot from long down hill or dragging the brakes while riding. Fluid heats up and expands and applys the brake, old fluid with water does it worse.  May have also had a rock or stick holding the pedal.  Trail fix is to dribble water on the caliper to cool it off.

Would that of caused the pedal to lock. I had to slam it to break it loose so I could use the brakes, then it got jammed again except that time it was applied. 

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Parker, let's start with the easy stuff first. 

Remove your brake pedal, see if the pivot is dry. If so, re-grease it.

Next thing, did you switch to a new MX boot? (They can be so rigid when new, that dexterity is all but impossible.)

One other thing to check when your pedal is diss connected from your M/C plunger...check for "free" movement of said plunger. (You have to remove the caliper from the disk for this.)

Let's see where we are after these. I kinda hesitate to go "into an M/C" over the internet. Youtube might assist in this, if needed. 

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As others said above, see if any mechanical binding with mechanism disco'd at different points.

Change fluid, pull rear caliper apart, inspect, replace as required, relube all contact points, bleed, and return to service. Don't forget to check rear disc runout if an over temperature issue occurred.

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2 minutes ago, Burnrider said:

You don't have enough play in the lever. It drags the shoes and heats the fluid til pads lock up. They get hot enough to melt vinyl at the caliper fitting. I have the right amount of play. My rotor is a little warped so that is causing the pads to heat up I think. I’m going to replace the fluid and grease the pivot. 

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