Brake bleeding suggestions?

[Dirt-Mink]

Hey guys.. I did a complete rebuild of my 86 honda xr250r brakes and im having some difficulty trying to put fluid back in the system... how does one remove all the air when that's all thats in there??

[kodey]

I had problems bleeding brakes befor to. I would take off the piston and pump. Then once the caliper is full. Crack the bleeder valve and push the piston back in. I know its not the right way but its fast and easy

[The Spanky]

First, use a syringe to fill the caliper and line with fluid.

 

Then reverse bleed them.

 

Take the top off the reservoir, and suck all the fluid out with a syringe. 

 

Tap the brake line with a tool, starting at the bottom and working your way up to the top to loosen any stuck air bubbles. 

 

Grasp the rotor on both sides of the caliper with your hands, and put your thumbs against the caliper. Slowly press the caliper towards the rotor to depress the piston back into the caliper. Slowly, or you will take a brake fluid shower!

 

Keep pressing until the piston bottoms out.

 

Suction the rest of the fluid out of the reservoir, refill with new fluid, and pump up the brakes, being careful to keep enough fluid in the reservoir that you don't run out and get more air into the lines.

 

The reason reverse bleeding works is because the air wants to rise. Normal bleeding with the brake lever moves very little fluid per pump, not enough to move an air bubble all the way from the top of the brake line to the bleeder screw in one pump. So every time you release the lever, the bubble rises back up, and you never get any where. But with reverse bleeding, the natural tendency for the air to rise works with you, because you are also pumping the fluid up, and pushing the caliper piston in moves much more fluid than pumping the brake lever.

[Dirt-Mink]

Ok awesome that worked great actually! But now there's a new problem... my brakes dont seem to let go on the disc. So I can spin the tire but its hard. And when I apply the brake it does work. Whats wrong now?

[The Spanky]

Ok awesome that worked great actually! But now there's a new problem... my brakes dont seem to let go on the disc. So I can spin the tire but its hard. And when I apply the brake it does work. Whats wrong now?

 

 

Some drag is normal, especially if the pads and rotor are new.

 

If you think it's excessive, maybe the caliper pins need some lube, or the pad retainer pins are grooved. Did you replace them?

[Dirt-Mink]

No I didnt replace the caliper pins. I have two sets though. Can I sand it smooth and lube it with lithium grease?

[The Spanky]

No I didnt replace the caliper pins. I have two sets though. Can I sand it smooth and lube it with lithium grease?

 

 

Generally the caliper pins (the ones under the rubber covers that the caliper slides back and forth on) don't get grooved, they just need to be cleaned and lubed with high-temp grease.

 

The pad retainer pins are the ones that get grooved from the pads being pressed against them. If they have any grooves that can't be cleaned up with something like a ScotchBrite pad they should be replaced. I usually replace them at least every other time I replace pads, they tend to be a pretty high wear item. Replacement pads usually come with replacement retainer pins.

Edited May 7, 2014 by Chokey

[Dirt-Mink]

So the pin im holding should be replaced? I can easily replace these without brake bleading right?

[The Spanky]

Yes, lube them with high-temp grease (they have little packets of it at the counter of most auto parts stores) and replace them.

 

No, you won't have to bleed again, you aren't opening the hydraulic system.

[Dirt-Mink]

Awesome! Thank you so much chokey! Your a life saver?

[Dragon67]

Awesome! Thank you so much chokey! Your a life saver?

 

Careful here.  The key word is "some" drag may be okay.  That wheel should spin pretty free for a few revolutions without binding.  If it doesn't, your caliper pistons may be gummed up so they can't fully retract.  This will be most apparent with new pads, because the edge of the pistons are used to being pushed father out as the old pads got thinner.  Too much brake fluid is bad, too, so don't overfill the MC.  If your calipers check out, and the pistons are not sticking, and the fluid level is good, maybe consider checking your spacers.  On some bikes the left and right are different sizes.  Just be careful with a wheel that doesn't spin easily.  Nothing good can happen if the front brakes lock up on you . . . speaking from recent personal experience. ?

[Dirt-Mink]

Thanks Dragon67! Ya my wheel wont spin at all.. im really hoping its not the pistons as I just went through a lot of trouble doing everything haha. Im going to try new pins and if that doesn't work... well im honestly giving the caliper to a shop because I have bad luck with brakes... my last front disc brake went south really quick when I played with it

[trailrydr9]

There may be some adjustment at the lever also. There should be a small knob or adjustment screw.

[LovingOffroadPain]

Here's my process.

1. Remove master cylinder cover. Fill to brim with DOT4 fluid.

2. Install 8 mm wrench and air vent hose from gas cap onto bleed valve on caliper.

3. Pump brakes 3 times, hold tight while cracking bleed valve. Lever will depress all the way to handbar, hold tight til bleed valve is closed.

4. Pump 3 times, and repeat.

You'll see air eventually come out the vent hose that's on the bleed valve if it's clear. Reverse bleeding as posted is an option too.

[LovingOffroadPain]

nothing good can happen if the front brakes lock up on you . . . speaking from recent personal experience. ?

Happened to me first ride on my KDX when I bought it at age 17. Met a guy who helped me bleed brakes for the first time as I described here.

Yea that guy who helped me turned out to be a drug addict. Looked him up years later, called his house but his sister called me back and said he was dead at age 40. Sad thing.

[Dirt-Mink]

Thats a sad and odd story loving... either way dont do drugs! Haha. Thanks for all the suggestions guys. Im gonna look thriugh all of them and try them!

[Qqqqqqqqqqqq]

I use the Syringe ( Back Bleed ) to get fluid into the system , next .. I use a vacuum pump to remove any air .

Works well

[thejunkman]

I have a video for this.

 

http://www.thejunkmanadv.com/how-to-brake-bleedingflushing-tutorial.html

[Dragon67]

Thanks Dragon67! Ya my wheel wont spin at all.. im really hoping its not the pistons as I just went through a lot of trouble doing everything haha. Im going to try new pins and if that doesn't work... well im honestly giving the caliper to a shop because I have bad luck with brakes... my last front disc brake went south really quick when I played with it

 

 

You'll save some dough and learn something if you do it yourself.  Probably one of the easiest jobs you can do.  That said, peace of mind is always a good thing.  If the wheel doesn't spin, do not ride the bike.  

[Dirt-Mink]

Well I figured if the wheel dont spin dont ride the wheel ? hahaha. But I ordered new pins so if that doesn't work with some grease ill buckle down and replace the piston seals and boots and such