Brake fluid change

Hi guys. Anyone can guide me thru the painfull procedure of draining the old brake fluid and get the new in? I already have air in the circuit and its really hard to take it out of the circuit... Thanks

 

Its not painful at all. Fill up your master cylinder with clean fluid and bleed the brakes. Keep the M/C full with clean fluid and keep bleeding until the fluid coming out of the caliper is clean and clear. It should take less than 30 minutes to do. This should be done every few years on any motorcycle to keep breaks operating properly .

 

+1

 

You bleeding it by pressing the brake, right? So you keep it pressed until the clean fluid start to bleed thru the system...

 

Sort of -- but you're forgetting to close the bleeder and will suck in air. Here's the order:

1. Put fresh fluid in reservoir
2. Slowly squeeze lever a few times then hold it
3.open bleeder to let Fluid out, then close bleeder before releasing lever, double-check fluid level in reservoir and top off as needed
4. Repeat steps 1-3 above
5. Again
6. And again
7. Etc til clean fluid is flowing

As I said before, Always close the bleeder before releasing the lever otherwise you'll draw air into the caliper.

 

+1 for hogfiddles,

I just add some clear tube to the bleeder screw to direct the fluid and also see air or change in fluid color. If you have never done this before to your bike I would suggest putting some penetrating oil on the screws holding the brake master cover, they can be a pain.

Rags under the brake master would be a good call as well, the fluid can stain and or damage paint if not washed off after the job.

 

Thanks a lot...I will follow the steps and the advices this sunday and I let you know....thanks

 

I'm having trouble with bleeding the brake as well. Rebuilt the master cylinder and the caliper cylinder. Couldn't get the air bled out. Disassembled and checked the master cylinder and it's working fine. Took the master cylinder off and put the old brake hose on and went right to the caliper cylinder. Bled out fine. Reassembled and now can't get the air out again. Suspect I have air trapped in the coupling on the bottom triple tree. (With the two banjo fittings) Tygon hose from the bleeder to a mason jar, forks turned so the bleeder is at the top, pumped nearly a full bottle of fluid through the dang thing and still have air trapped somewhere. De-fusing my attitude before before pulling the fitting off and trying to bleed off there. Been bleeding brakes for nigh on 60 years, but this has kicked my butt!

 

Welcome to the forum Alan.
Have you tried using a syringe and bleeding from the bottom up?
There also is a method of using a Palm sander (without paper), to induce a vibration from the bottom up of the brake system to break up/ remove micro bubbles of air that like to cling to the inside of fresh new brake lines.

 

Both excellent ideas. I hadn't heard of the sander trick, but that's worth a try first as it's so easy. Tks.

 

Wow never heard of the sander trick, just a powered version of hitting it with a wrench or screw driver.

Just want to make sure you are bleeding the farthest line first (if you have double front brakes) that will help with the air. When you are bleeding is the bike on the center stand or is it leaning over? The only other two tings I can think of is a vacuum system and the over night trick of tapping of clamping the lever to the bar. This will allow the trapped air to escape over night. Good luck.

 

think about this, if there is a bubble in the line, if it's not moving down, it's moving up. if you do the "open squeeze close release " that bubble only moves down on squeeze. the rest of the time it's going back up. this works great on cars because the lines are horizontal.
now teflon on bleeder, clear hose on bleeder into jar
try this, but watch out for the squirt that comes from the mc. quickly squeeze the lever and let it snap back, notice more fluid came out than was drawn back in
you can do this fast enough to keep the bubble moving down

 

My front brake is real spongy and I opened the MC today to find fluids brown and full of contamination . Gonna run fluid through first normally to get old fluid out ,then Ill use syringe method to get air out . I always did this on mountain bikes with no problems. Otherwise I end up sitting hitting calliper with wood block to get bubbles to move .

 

Finally got the air out of the brake lines. Took the banjo off the MC, forced 2ml from the bottom up with a syringe, tapping the line to help loosen any air bubbles. With the MC banjo just barely loose I forced some more fluid from the caliper up. Then pumped the MC with the banjo loosened again and everything is just peachy. Except for the two oil pigs I filled up with brake fluid!