Brake Bleeding

Is there a brake bleeding for dummies instruction somewhere? I am a total noob and need some step-by-step instructions.

I looked in the FAQ but did not see one.

 

Brake bleeding is a general process that is basically the same on every hydraulic brake system. Open valve, squeeze, close valve, release, repeat.

You can get more details if you do a search for 'brake bleed' on this site or on google.

Do you have any questions about where components are on these bikes specifically or what equipment to use? There are some common problems that tend to crop up on these bikes. If you have any trouble let us know.

 

Simple old-school bleeding:

Set an 8mm box end wrench on the bleed nipple in position where it will have clearance to turn CCW and open the valve; attach a piece of clear tubing to the bleeder and submerge it in some clean brake fluid (about 1" worth) in a suitable container.

Get your master cylinder as level as possible, and pop the cap, ensure brake fluid is topped off. Set cap back on. Wrap a rag or shop towel around the M/C to catch any spillage.

Gently pump the lever three or four times to build up pressure.

Open bleed valve and gently squeeze lever. When it has collapsed almost all the way against the bar, close the bleed valve. Release brake lever, and gently pump three or four times to build up some pressure.

Repeat.

Every two or three "bleed cycles" check your fluid. If the M/C sucks wind you have to start over and may trap a bubble.

Repeat until you see no more bubbles in the clear tube coming out of the caliper.

Tips: A vacuum pump such as a Mity-Vac can be a big help, but I always do the final bleeding by hand as described above.

The bleed nipple can sometimes allow air to be pulled from outside past the threads, making you think you've still got air in the system; a couple of turns of teflon tape on the threads will fix this but be sure not to block the hole.

Refilling and bleeding a dry system on one of these bikes especially if you've just rebuilt the caliper and master cylinder and replaced the lines, can be an exercise in frustration; it takes a while to say the least. This is when the Mity-Vac really comes in handy.

When bleeding a dry system, it may be necessary to "crack" open the various pipe junctions in the system to release trapped bubbles you may never get out otherwise.

Once you've managed to get everything right, re-bleed the system after a couple hundred miles. A few heat cycles will boil out any micro-bubbles, and you'll get a bubble or two on the re-bleed.

 

Thanks for the tips, guys.

Yes, I just rebuilt my master cylinder.

I did buy a Mighty Vac from Chacal.

I am off to buy some fluid and give it a go.

 

Buy the big bottle. DoT3. Don't "recycle" fluid that's been bled out, discard it.

 

Update. I worked on bleeding for a bit and then took my car to a mechanic for a brake job. During the brake job he flushed and bled my car brakes.

Talking with him I think my XJ650 is experiencing air getting in the threads of the bleeder screw.

I tried to buy some thread tape and the auto parts store was out of stock.

I am going to get some thread tape and try to tape the threads of the bleeder screw.

Failing that I will take the bike to the mechanic who did my car. We play in a church band together and he lives fairly close. He has done motorcycle brake bleeding so I should be in good hands.

Thanks guys.

 

Sucking bubbles past the bleed screw threads is exacerbated when you use a Mity-Vac; it was driving me crazy until I used the teflon tape.

Another reason for doing the final bleed by hand.

 

I get zero grab on the brake lever and tons of bubbles are getting past the threads using the mighty vac.

As soon as I can get some tape I will probably make some progress.

Thanks for the advice.

 

it was taught in tech college and various bendix brake classes. pumping the brake before bleeding results in bubbly brake fluid creating more air to the air already in the system.

on cars. you press brake pedal. open valve. close valve. release pedal. press pedal and do over again. the procedure is more critical with ABS brakes.

bikes can be more of a pita.

DOT4 is ok to use. DOT3 is getting harder to come by around here.

 

My Brake Bleeding Procedure is:

"Old School, ... with a Twist"

With the Bleed Screws wrapped tight with Teflon Tape, ... I connect a:
ONE-MAN BLEEDER
(( http://www.summitracing.com/parts/OTC-4599/?rtype=10 ))

With the One-Man Bleeder attached to the Bleed Nipple and it's One-Way Valve --> SUBMERGED <-- in Brake Fluid, ...

I slowly PUMP the Brake Lever and Watch what EXITS the System.
When all the Air Bubbles and Brake Fluid COMING OUT ... is Fresh Clean Brake Fluid ... the Flushing and Bleeding of the System is quite easily accomplished.

PROVIDING THAT ... The Brake Master Cylinder is Healthy and its SEALS are functioning properly. The Brake Fluid needs to be Pumped OUT of the Master Cylinder with each grab of the Brake Lever.