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Discussion Starter · #1 ·
I need a little help, every time I go out for a ride my bike rear brake locks up after 10 minutes of riding. I already bled the brakes but I’m not sure if I did it right it began to squeak after I bled them. When the temperature gets to about 220 is when I begin to notice the Brakes locking up.

Somebody please help I’m new to all of this.
 

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Your engine temperature goes up to 220°F? That is very high. Normal operating temperature is around 180°F unless you're in a hot climate.

In any case, your brake systems are independent of your engine. If your rear brake locks up inspect your rear brake only. Your problem points to a stuck brake piston likely due to corrosion.
I would recommend a new piston and seal set for the rear caliper, around $40 I believe. You can do this yourself if mechanically inclined and you have a tool or compressed air to get the stuck piston out. You may want to have a shop do it since it's a fairly quick procedure for a mechanic.
 

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Most likely corrosion in the caliper groove where the seals sit. This forces the seals onto the piston which means it doesn't retract as it should after the brake pedal is released.

The rear caliper is a fairly easy rebuild if you fancy doing it, but you need to make sure you get all the white powdery corrosion and gunk out of the groove the seal sits in, or the brake will just stick on again. A soft brass brush in a Dremel works well if you go gently. Then fit fresh seals.

The piston is stainless steel in the rear caliper so can be cleaned up with brake cleaner and one of those green pan scouring pads. Clean up the caliper sliding pins and re-lubricate with silicone brake grease.

Just be methodical and keep everything clean (have lots of paper towels handy for wiping), and you'll get there. If you're not confident, have a shop do it.
 

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I have a similar issue. The fact that it does it after riding awhile makes me think heat is a factor also. Possibly the piston heats up and expands, causing it to stick in the caliper, in addition to the system being gunked up.
 

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If the brake gets locked after some riding, it is most probably due to a brake pad dragging all the time against the rotor: this heats up both metal and brake fluid, seizing the whole brake.
I have seen this happening on my son's 125cc a few years ago.

Can't tell without seeing if it is due to the caliper piston not retracting or anything else (gunk, watered braked fluid, corrosion etc...) , but servicing/rebuilding the complete caliper seems a good suggestion to me.
 

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Find the parts fiche for your year/model on here,


and make sure all the components have been fitted correctly.

As per other posts there may be corrosion on the pistons. Take the caliper off and apply the rear brake pedal to move the pistons out but be careful not to pop-them fully out and look for corrosion. If found polish it out with some 1200 grit and then polish them with Metal polish. Then blast with carb/brake cleaner to make sure they are clean. I lube mine with ACF50 or PTFE lube. I use High-Temp or red-Brake grease on the float pins,

USA


UK
Red Brake Grease

Which can also be used to lube the pistons if used sparingly.

I use a C-Clamp with some masking tape on the faces to push the piston/s back in before refitting the caliper.

Once back on the bike and if you have an air compressor you can try draining the fluid and with the bleed nipple removed blast down through the Reservoir whilst operating the brake pedal to make sure there's no debris blocking any small holes or the line. Then re-fill and bleed possibly a couple of times.

Hopefully you don't have a warped Rear-Disc but if you do they are not super expensive to replace.

HTH :)
 
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If the brake gets locked after some riding, it is most probably due to a brake pad dragging all the time against the rotor: this heats up both metal and brake fluid, seizing the whole brake.
I have seen this happening on my son's 125cc a few years ago.

Can't tell without seeing if it is due to the caliper piston not retracting or anything else (gunk, watered braked fluid, corrosion etc...) , but servicing/rebuilding the complete caliper seems a good suggestion to me.
This is spot on.

I only took a pic of my front caliper pistons but this is a before/after cleaning and what was inside the caliper too but the rear caliper was in the same condition. Servicing them is not that difficult.
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I had something similar recently, not my sv but turned out to be a perished brake line had swollen internally, building pressure over several operations and releasing after sitting a bit. Not the first thing I looked at.
 
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