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Discussion Starter #1
Hello, I am Dorus and I am new here to the forums. I recently bought a Honda XRV750 RD07 as my first bike.
I noticed that my front brakes are dragging and I am worried that it really impacts my fuel economy. I've looked around the internet and found some videos how fix it. Do you guys think it's a good idea to try fix it the as explained in the videos for the AT?

My front brake is dragging like in this video:
https://www.youtube.com/watch?v=KWjZRqP-Bro

And I think I want to fix it, like it's explained in this video:
https://www.youtube.com/watch?v=hfqpPO-Z1Zo

Cheers,
Dorus
 

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Dragging brakes brakes can have two causes.

Swollen brake lines that act as one-way valves and won't release pressure.

Pistons sticking within the caliper. Often caused by corrosion setting in the grooves where the dust and oil seals are located. That corrosion pushes the seals onto the pistons and keep them from fully retracting. You need to rebuild your calipers and clean the grooves with a metal pick. This is the usual cause of dragging brakes. Check pistons to see if they are pitted. You can polish them on 800 or 1000 grit wet sand paper to remove dust and gunk. If they are pitted, then replace them.
 

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Have you tried bleeding them yet? Air in the fluid can cause brake binding, and as they can be a bit fiddly to bleed properly, it's quite common. Unless you're sure it's been done recently, it's always worth flushing the brakes on a new (to you) bike, and it doesn't cost much.

If they still bind, it's time for a strip down, and there are plenty of threads on here about how to do it. The calipers are made of low-grade cheese, so some corrosion is almost inevitable, but they aren't difficult to strip. The critical areas are the grooves for the dust seals and the piston seals (as well as the pistons); the alloy the grooves are cut into gets eaten away on bad cases. They can be repaired by a specialist, and there are a few threads on here about them. Getting good second-hand ones is difficult, as they all tend to have suffered a bit. Regular strip-and-cleaning is the answer, so best learn how to do it this time. Good luck:thumbup:
 

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Discussion Starter #5
Dragging brakes brakes can have two causes.

Swollen brake lines that act as one-way valves and won't release pressure.

Pistons sticking within the caliper. Often caused by corrosion setting in the grooves where the dust and oil seals are located. That corrosion pushes the seals onto the pistons and keep them from fully retracting. You need to rebuild your calipers and clean the grooves with a metal pick. This is the usual cause of dragging brakes. Check pistons to see if they are pitted. You can polish them on 800 or 1000 grit wet sand paper to remove dust and gunk. If they are pitted, then replace them.
Have you tried bleeding them yet? Air in the fluid can cause brake binding, and as they can be a bit fiddly to bleed properly, it's quite common. Unless you're sure it's been done recently, it's always worth flushing the brakes on a new (to you) bike, and it doesn't cost much.

If they still bind, it's time for a strip down, and there are plenty of threads on here about how to do it. The calipers are made of low-grade cheese, so some corrosion is almost inevitable, but they aren't difficult to strip. The critical areas are the grooves for the dust seals and the piston seals (as well as the pistons); the alloy the grooves are cut into gets eaten away on bad cases. They can be repaired by a specialist, and there are a few threads on here about them. Getting good second-hand ones is difficult, as they all tend to have suffered a bit. Regular strip-and-cleaning is the answer, so best learn how to do it this time. Good luck:thumbup:
Thanks for your information!

I haven't tried bleeding them yet. And I've never done that before, the fluid still looks pretty good through the inspection glass and I have good breaking power.

I'll try to bleed them with some new brake fluid and a drain hose and see if that makes it any better. Also, I'll try to inspect the brake pistons for corrosion before taking the whole brake callipers apart.
The brake discs still look super good, can't find any tiny grooves in it. So I hope it's not too bad.

Cheers!
 

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Air, unlike brake fluid, is compressible. Therefore, even if the brake lines were were 100% filled with air, it wouldn't affect the pistons.

Don't waste your time bleeding the brakes. Have your calipers rebuilt. But as a last test, put your bike on its centerstand and jack the front wheel. Spin it. if it drags, then unscrew the bleed valves. if it releases some pressure, the wheels would now spin freely, and you have just found that the problem was with the brakelines. This test is easy to do.

If you are not mechanically inclined, have a pro rebuild all three calipers.
 

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the sliding bush that sits in the rubber boots on one of the mounting bolts can get rusty and cause binding if a donkey goes to town on a bike with a power washer they wash the grease out of everywhere . its a good idea to check your wheel bearing's and sprocket carrier for grease too also your swinging arm linkage . its a good idea to coat your pistons with copper grease after polishing them to prevent rust from road salt . you should buy yourself a Haynes workshop manual and a torque wrench . good luck with it .
 

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Discussion Starter #8
Air, unlike brake fluid, is compressible. Therefore, even if the brake lines were were 100% filled with air, it wouldn't affect the pistons.

Don't waste your time bleeding the brakes. Have your calipers rebuilt. But as a last test, put your bike on its centerstand and jack the front wheel. Spin it. if it drags, then unscrew the bleed valves. if it releases some pressure, the wheels would now spin freely, and you have just found that the problem was with the brakelines. This test is easy to do.

If you are not mechanically inclined, have a pro rebuild all three calipers.
the sliding bush that sits in the rubber boots on one of the mounting bolts can get rusty and cause binding if a donkey goes to town on a bike with a power washer they wash the grease out of everywhere . its a good idea to check your wheel bearing's and sprocket carrier for grease too also your swinging arm linkage . its a good idea to coat your pistons with copper grease after polishing them to prevent rust from road salt . you should buy yourself a Haynes workshop manual and a torque wrench . good luck with it .
Thanks for the information again,

I've put the bike on its centre stand and jacked the wheel, the wheel is dragging like in the first video I've linked. I'll check if there's too much pressure in the brake lines as soon I have some sort of bleed hose.
I've just found a PDF of the Haynes workshop manual and it looks doable. I think I'll just get some new brakepads aswell while I am checking the cilinder of the brakes.

Thanks!
 

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I bough new seals and pistons and ebc hh sintered pads for my transalp when it was just a stuck sliding bush probably there was a lot of rust in there a good sand down and grease sorted it . I got economy pistons from wemoto they were rubbish rusted away to nothing after 2 years winter riding the chrome was flaking off them . good job I kept the old pistons cleaned them up and stuck them back in . the pads have lasted well 23000 kms and still a bit left . I tend to not brake much though just let off the throttle in time and I live out in the sticks .
 

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I rebuild these weekly..

I always polish the pistons until they are like a mirror. But i have a polishing machine.

The grooves for the new seals need to be cleaned thoroughly too..

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The grooves for the new seals need to be cleaned thoroughly too..
Indeed. I use a metal pick for that. is there a dedicated tool that works better?
 

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Indeed. I use a metal pick for that. is there a dedicated tool that works better?
My late father was a dentist so I inherited a tool box full of very high quality hardened dental picks of all shapes and sizes. I use them a lot for all types of things. Inc cleaning grooves. :)



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I just make a little scraper out of a piece of a wash up liquid bottle off the bottom with the right angle in it . I read on hear probably that a metal scraper has to used very gently so as not to do damage . I don't have one myself the bit of plastic works fine I spray in a bit of brake cleaner to wash out the grooves for the seals .
 

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I just make a little scraper out of a piece of a wash up liquid bottle off the bottom with the right angle in it . I read on hear probably that a metal scraper has to used very gently so as not to do damage . I don't have one myself the bit of plastic works fine I spray in a bit of brake cleaner to wash out the grooves for the seals .
Plastic is nowhere near hard enough for some of the callipers I restore.

I have never damaged a calliper yet with steel tools.

The alloy is actually quite hard. If not, then it is very corroded and should be replaced anyway.

You are right though..Care is always required with brakes..



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I too have stripped my front callipers a number of times when the discs have started to drag badly. Its always been a powdery corrosion in the dust seal grooves which has caused the seals to pressure the pistons (I also use a dental-type pick to clean them out). Pistons get cleaned with Autosol. Using new OEM dust seals seems to have slowed down the need to strip them as compared to aftermarket seals.
Interestingly, I've never stripped the rear calliper which continues to work fine with no binding whatsoever.
One other cause of binding, aside from sticky calliper pistons, can be a sticky master cylinder piston albeit this seems to be a relatively rarity.
 

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This worries me, working on items such as brake calipers and wheel bearings, although fairly simple if you know what your doing and have the correct tools to carry out the task are systems that are 100% critical safety related and should be left to competent persons to service!
I know we all use the forums to pick each other's brains and save ourselves paying for maintenance costs but learning to repair this type of critical system should be learned under supervision. I wonder how many brake issues for these bikes are caused by incorrect home repairs?

Sorry rant over:rolleyes:
 

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I wonder how many brake issues for these bikes are caused by incorrect home repairs?
None in my case. And I wouldn't trust a shop mechanic to touch my bikes... :D
 
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