BMW R850 Maintenance Manual page 44

After the fluid has been completely replaced and all nipples are tight, check that the
front and rear reservoirs are filled and secure. Slowly pump the front brake lever, then
pump the foot pedal until there is a solid feel. Continue pumping the brakes for a few
minutes, then recheck the reservoir level and refill if necessary.
WARNING: You must pump both front and rear brakes to confirm that they are
responding with a solid feel BEFORE you ride the bike!!!
Note on brake fluid level: Before replacing brake pads, remove brake fluid so that it is
NOT at the maximum level. New brake pads will take up some of the brake fluid space
in the system; if the brake fluid is at maximum level it probably will overflow the reservoir.
METHOD TWO.
No Mityvac is used in Method Two. This method is used by many auto mechanics who
use the brake master cylinder to create the pressure needed to force fluid through the
brake lines. You will not be using the suction created by the Mityvac.
Replace the fluid in the handle-bar mounted reservoir as described in Method One.
There are still four basic steps in Method Two, but number one has been changed. The
steps now read: (1) Keep the reservoir cover in place to prevent fluid from squirting up
(which will create havoc with your paint) and attach a drain tube and jar to the caliper
nipple to catch any fluid that will be drained from the nipple. Pump the brake lever to
insure that the system can create pressure. Now, pull the lever gently (as in applying
the brake) while you perform the next two steps. Do NOT allow the lever to return to its
open position until the next two steps are complete!!! (2) Gradually open the bleeding
nipple at the disk caliper approximately 1/2 turn (3) Close the bleeding nipple while fluid
is STILL COMING OUT and BEFORE the reservoir is empty, (4) With the caliper nipple
closed and the reservoir cover still in place, release the lever. Understand and memorize
step #3. With this method you are replacing the brake fluid one "squirt" (i.e. one press of
the brake lever) at a time and repeating until clear fluid emerges from the drain tube
connected to the bleeder valve. Keep an eye on the reservoir during these steps and
refill whenever it goes down to 50%.
Be extremely careful with the bike's brake fluid in the handle-bar mounted reservoir!!!
Follow the same procedure that is described in Method One. Start on the left front and
bleed the fluid until it is clear in color. You must close the bleeding nipple to turn off the
flow by tightening the nipple while the fluid is still coming out, and this means
maintaining a small amount of pressure on the brake lever and maintain some fluid flow.
If you take the pressure off the brake lever while the fluid is still coming out, you may
introduce air into the brake system and this is bad. Read "Air in the System" below.
(You may be able to locate a "One Man Brake Bleeder" which is a one-way valve that
attaches to the bleeder nipple and prevents air from entering through the bleeder nipple.
When using this, instead of opening and closing the bleeder valve, you just pump the
master cylinder until the fluid runs clear and being careful to keep brake fluid in the
reservoir. Do not let the reservoir run dry; this will pump air into the system.) You are
finished with the left side when discharging fluid is clear and the caliper nipple is tight.
Repeat this procedure with the front right caliper. Make certain the front brakes are
finished, the front nipples are tight, and the front reservoir cover is secure with the four
screws. It is now time to bleed the rear brakes using the same procedures.
44