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Remove
the front brake system in it's entirety from the bike, intact. Unbolt
the caliper from the fork, the master cylinder/lever assembly from the
handlebar, and unclip the hose. Don't crack the bleeder or the
master cylinder cap, keep the system shut. Then arrange the system
so that the bleeder nipple is lowest, the part where the brake hose
leaves the caliper is a bit higher, the hose is sloped uphill to the
lever, the spot on the master cylinder where the hose connects is higher
still, and the spot on the inside of the master cylinder where the juice
goes in is highest. I used my vise on my bench and a series of
stacked things next to my bench like cinder blocks, chairs, blocks of
wood and what not. Keep in mind the nasty corrosive nature of
brake fluid when choosing things to put under your brake system.
Get a great big monojet syringe. Agricultural supply places and
feed stores have them. I have one that holds 300cc, which is about
five times what your brake system holds. You want to connect this
to your bleeder nipple, so get clear aquarium tubing or clear PVC tubing
at the hardware store and whatever connectors you need to connect the
syringe to the nipple.
Fill the syringe with fresh brake fluid, and fill the connected hoses
with fluid too. Attach the hoses to the bleeder nipple.
Get ALL the bubbles out of the tubing and the syringe.
There can be air at the plunger end of the syringe as long as you
hold it plunger-up and don't squirt so far that it enters the hose.
Once all the bubbles are out of the tubing and syringe, crack the
bleeder nipple and gently plunge new fluid into the system. It
should push all the old fluid, and your bubbles, out through the master
cylinder. The master cylinder resevoir will over flow, so have a
helper there to suck it down with another syringe, or have a bunch of
rags there to catch the overflow, or have stuff under the master
cylinder that you don't care about.
Some calipers have chambers that can have high internal cavities that
will hold air the way air will stay in an inverted glass underwater.
The bleeder valve SHOULD be the highest point on the inside of a
caliper cavity, but it sometimes isn't. So, as you are plunging
the fresh fluid into the caliper, without letting the hose come off the
nipple, roll and rotate the caliper around so that any internal trapped
bubbles can make their way to the bleeder valve and on out through the
brake hose and out the master cylinder resevoir.
If you run out of juice in the big supply syringe while you're doing
this, just shut the bleeder valve, pull the plunger out, add more juice
to the supply syringe and re-insert the plunger. If you do this
right, no air will enter the hose at the bottom of the syringe, and you
can continue to pump juice through the system.
After you've pumped a bunch of fluid through, shut the bleeder valve and
button up the master resevoir. Clean everything up and re-install
on the bike. If you did it right, and this doesn't do the trick,
then you have some other problem, such as a faulty hose that's
expanding, a warped disc, or bad rubber in your master cylinder or
caliper.
Keep in mind that fresh pads sometimes need to "take a set" or
break in. They don't exactly mate with the disc and have to rub off just
a bit of material. Riding 100 yards with your brake held on can
accomplish this. Brand new pads that need to take a set feel just like
air in the line.
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