front brake bleed for an airhead

[Stan_R80/7]

I found simply opening the bleed screw and letting gravity drain all the brake fluid works for me. The MC needs to be watched so it does not run out of fluid. But, the technique does take some patience.

For those with no patience, the mity-vac, the syringe technique, pumping the handle to build pressure - hold and bleed, speed bleeders, and pressurizing the master cylinder are alternatives. Having tried them all, I use what works for me. Good luck!

[bmwhacker]

If you change out all the fluid (which you should) you could encounter an "air lock" in the master cylinder.
I struggled with that for an hour or so when I rebuilt my under tank master cylinder. I ended up taking a small syringe and injected brake fluid directly into the orofice in the master cylinder through the reservoir cap. Somehow that got the air chased out and then the system bled out without any problems.

[DaveBall]

I change the brake fluid on all my bikes every winter, as a part of my regular maintenance. This serves 2 purposes to me. First, I check over every bit of the braking system to ensure no leaks, kinks or rock gouges in the lines and to ensure that I will have little to no braking issues during the rest of the year riding.

As I have stated before, in many previous threads, I find it easiest to reverse bleed. I first remove as much fluid as I can from the master cylinder using a syringe. If it is a new to me bike, I try to suck up any bits and crap that may be at the bottom of the m/c. Otherwise it is usually pretty clean. I then use another clean syringe to force new fluid up from the bleeder in the caliper. Slowly force new fluid up into the m/c and when it gets full, I then remove a bunch again til I can force more up thru from the bottom. This helps to remove as much air as possible. Even after only having the fluid in for a year, you can tell when the new fluid is coming thru. Because I am cheap, I keep the syringes and tubing for the next time by putting them into a clean zip lock bag on the shelf, next to the fluids. As the syringes are pretty inexpensive to buy at the local pharmacy, you could just toss them and buy new when you next need them.

It is a simple, one person job that has worked for lots of people for a lot of years. Even works well if you have just rebuilt or replaced any part of the brakng system. So much faster to remove the air from a newly rebuilt set of calipers.

[boxerboy81]

iF YOU KNOW ANY NURSES, THEY CAN GET ONE FOR YOU. pLACE AN ORDER FOR A CATHETER TIP SYRINGE. oops...just don't ask what it was used for!



Whilst your nurse buddy is getting the syringe, also ask for some used oxygen tubing with smooth bore ends. Works a treat. There is a type of oxygen tubing that comes in 50ft lengths that can be cut to size, and has variable id to enable better fit to oxygen outlets. It's ideal for the catheter tip syringe, and is smooth bore so that the connection to the catheter is airtight. This stuff gets chucked everyday in huge lengths. Just soak in ammonia for 10 minutes for your own safety.

[sigpe57]

Originally Posted by DaveBall

I change the brake fluid on all my bikes every winter, as a part of my regular maintenance. This serves 2 purposes to me. First, I check over every bit of the braking system to ensure no leaks, kinks or rock gouges in the lines and to ensure that I will have little to no braking issues during the rest of the year riding.

As I have stated before, in many previous threads, I find it easiest to reverse bleed. I first remove as much fluid as I can from the master cylinder using a syringe. If it is a new to me bike, I try to suck up any bits and crap that may be at the bottom of the m/c. Otherwise it is usually pretty clean. I then use another clean syringe to force new fluid up from the bleeder in the caliper. Slowly force new fluid up into the m/c and when it gets full, I then remove a bunch again til I can force more up thru from the bottom. This helps to remove as much air as possible. Even after only having the fluid in for a year, you can tell when the new fluid is coming thru. Because I am cheap, I keep the syringes and tubing for the next time by putting them into a clean zip lock bag on the shelf, next to the fluids. As the syringes are pretty inexpensive to buy at the local pharmacy, you could just toss them and buy new when you next need them.

It is a simple, one person job that has worked for lots of people for a lot of years. Even works well if you have just rebuilt or replaced any part of the brakng system. So much faster to remove the air from a newly rebuilt set of calipers.

I tried the traditional squeeze the brake lever method and reverse bleed method. The brake still feels soft. I have the center-mounted front master-cylinder.

-Tap/Knock on the cylinder body?
-Remove the brake switch and bleed?
-Flip the master cylinder upside down?
-Leave it overnight and bleed again?
-Combination of the method above?

These are few advises but how does a professional repair shop do it? They probably can not afford to do the combinations above and expect to make money.

[boxerboy81]

Loosen the reservoir so that it can be tilted to encourage air to go where you want it. (Ate frame mounted reservoir and mc.)

[manic mechanic]

One place that can trap air is at the front of the M/C where the brake light switch is located. Remove the wires from the switch, squeeze the lever and loosen the switch slightly, after placing a rag under it. Then retighten the switch and check for pressure. Repeat as necessary.