contamination.

Airbag models:

[1]

– oil bolt (upper side) and sealing washers [1]
– upper side brake hose(s) [2]
– brake hose joint attaching bolt [3]

Non-airbag
models:

[1]

[4]

Loosen the oil bolt (front side).
Remove the following:
–
–
–
–

mounting bolts [4]
oil bolt (front side) and sealing washers [5] (discard)
front side brake hose [6]
secondary master cylinder [7] (discard)

[2]

[3]

[4]

[3]

[2]
[5]

[7]

[6]

PLUG THE BRAKE HOSES
Install the washers (reuse), oil bolts [1], and provided
cap nuts [2] to the brake hoses as shown.
Tighten the cap nuts securely.
[1]
[2]

8

GL1800 #23 - REPAIR PROCEDURE
TEMPORARILY REINSTALL THE
FRONT WHEEL
Temporarily reinstall the front wheel and hand tighten
the axle nut [1].
Temporarily reinstall the brake calipers and hand
tighten the bolts [2].
[2]

[1]

PEDAL BRAKE LINE FLUID FLUSHING
FLUID FLUSHING
• Use only the provided Pro Honda DOT 4 brake
fluid from sealed containers to ensure the
quality of the repair procedure.

[1]

• It is not a problem if the fluid flowing out of the bleed
valve contains air bubbles because the lines will be
bled in later steps (AIR BLEEDING).
Fill the reservoir [1] with only Pro Honda DOT 4 brake
fluid from a sealed container.
Operate the brake pedal [2] several times until the
brake fluid level in the reservoir goes down.

[2]

Connect a commercially available brake bleeder to the
upper side bleed valve [1] of the left front caliper.
Activate the brake bleeder and loosen the bleed valve.
• Check the reservoir fluid level often while filling the
brake to prevent air from being pumped into the
system. If air is entering the bleeder from around the
bleed valve threads, seal the threads with Teflon
tape.
If an automatic refill system is not used, add brake fluid
when the fluid level in the reservoir is low.

[1]

Repeat above procedure until a sufficient amount of
clean fluid flows out of the bleed valve.
Close the bleed valve.
• When using a brake bleeding tool, follow the
manufacturer’s operating instructions.

9

GL1800 #23 - REPAIR PROCEDURE
Perform the flushing procedure at each bleed valve in
the sequence as follows:

[2]

1. Right front caliper lower side bleed valve [2]
2. Rear caliper lower side bleed valve [3]

[3]
Manual pumping is
required to ensure
all contaminants
are removed from
the pedal brake
line.

Manually pump (no vacuum bleeder) another 200 cc of
fluid through each bleed valve in sequence; [1], [2], [3].

[2]

– Fill the reservoir to the UPPER level line.
– Pump the fluid through the bleed valve by operating
the pedal until the fluid comes down to the LOWER
level line.
– Repeat the procedure eight (8) times to pump about
200 cc (approx. 7 oz) through the system.
Use a graduated cylinder as a catch basin for manual
pumping to measure the amount of flushed brake fluid.
Drain the fluid from the system, with the brake bleeder
tool, through each bleed valve in sequence; [1], [2], [3].

[1]

[3]

TEMPORARILY REMOVE THE
FRONT WHEEL
Temporarily remove the front brake calipers and front
wheel.

10

GL1800 #23 - REPAIR PROCEDURE
INSTALL THE NEW SECONDARY
MASTER CYLINDER
Remove the cap nuts that were installed on the brake
hoses earlier.

Airbag models:

Non-airbag models:
[2]

Connect the front side brake hose [1] to the master
cylinder with the oil bolt [2] and new sealing washers
[3].

[2]

Install the new secondary master cylinder onto the fork
leg with the mounting bolts [4] and tighten them.

[6]

TORQUE: 30 N·m (3.1 kgf·m, 22 lbf·ft)
Tighten the oil bolt (front side).

[3]

[6]

TORQUE: 34 N·m (3.5 kgf·m, 25 lbf·ft)
[3]

Install the brake hose joint and tighten the bolt [5].
TORQUE: 12 N·m (1.2 kgf·m, 9 lbf·ft)
Connect the upper side brake hose(s) [6] to the master
cylinder with the oil bolt and new sealing washers, and
tighten the oil bolt.

[3]

TORQUE: 34 N·m (3.5 kgf·m, 25 lbf·ft)

[2]

[4]
[1]

[5]

REINSTALL THE
FRONT WHEEL
Refer to the Service Manual, reinstall the front wheel
and brake calipers.
Tighten all hardware to the specified torque values.
Do not reinstall the front fender at this time.

11

GL1800 #23 - REPAIR PROCEDURE

PEDAL BRAKE LINE FLUID FILLING
• Use only the provided Pro Honda DOT 4 brake
fluid from sealed containers to ensure the
quality of the repair procedure.
• Feed fluid into the pedal brake line in the following
sequence:
1. Left front caliper, upper side bleed valve [1]
2. Right front caliper, lower side bleed valve [2]
3. Rear caliper, lower side bleed valve [3]
4. Anti-dive plunger bleed valve [4]
5. Rear caliper, upper side bleed valve [5]
[1]

[5]
Left front caliper:

[3]

[4]
[2]

Rear caliper:
Anti-dive plunger:
Right front caliper:

FLUID FILLING
• It is not a problem if the fluid flowing out of the bleed
valve contains air bubbles because the lines will be
bled in later steps (AIR BLEEDING).

[1]

Fill the reservoir [1] with only Pro Honda DOT 4 brake
fluid from a sealed container.
Operate the brake pedal [2] several times until the
brake fluid level in the reservoir goes down.

[2]

12

GL1800 #23 - REPAIR PROCEDURE
Connect a commercially available brake bleeder to the
upper side bleed valve [1] of the left front caliper.
Activate the brake bleeder and loosen the bleed valve.
• Check the reservoir fluid level often while filling the
brake to prevent air from being pumped into the
system. If air is entering the bleeder from around the
bleed valve threads, seal the threads with Teflon
tape.
[1]

If an automatic refill system is not used, add brake fluid
when the fluid level in the reservoir is low.
Repeat the above procedure until a sufficient amount of
clean fluid flows out of the bleed valve.
Close the bleed valve.
• When using a brake bleeding tool, follow the
manufacturer’s operating instructions.
Perform the above procedure at each bleed valve in the
sequence as follows:

[2]

1. Right front caliper lower side bleed valve [2]
2. Rear caliper lower side bleed valve [3]
3. Anti-dive plunger bleed valve [4]
4. Rear caliper upper side bleed valve [5]

[3]
[4]

[5]

Manual pumping is
required to ensure
all contaminants
are removed from
the pedal brake
line.

Manually pump (no vacuum bleeder) another 200 cc
(approx 7 oz) of fluid through each bleed valve in
sequence:

[4]

1. Anti-dive plunger bleed valve [4]
2. Rear caliper upper side bleed valve [5]
– Fill the reservoir to the UPPER limit line.
– Pump the fluid through the bleed valve by operating
the pedal until the fluid comes down to the LOWER
level line.

[5]

– Repeat the procedure eight (8) times to pump about
200 cc (approx. 7 oz) through the system.
Use a graduated cylinder as a catch basin for manual
pumping to measure the amount of flushed brake fluid.

13

GL1800 #23 - REPAIR PROCEDURE

PEDAL BRAKE LINE AIR BLEEDING
MANUAL AIR BLEEDING
• Use only the provided Pro Honda DOT 4 brake
fluid from sealed containers to ensure the
quality of the repair procedure.
• Note that you may feel strong resistance on the
brake pedal during pumping to bleed air from the
right front caliper. This is caused by the activation of
the delay valve. Be sure to depress the brake pedal
fully to the bottom.
• The air bleeding procedure must be performed in the
same way as in the fluid filling procedure without
using a brake bleeder tool.
Repeat this procedure until air bubbles no longer
appear in the plastic overflow hose at each bleed
valve.
After air bubbles cease to appear in the fluid, repeat
the air bleeding procedure 2 to 3 times.
• Make sure that the bleed valves are closed and
operate the brake pedal. If it still feels spongy, bleed
the system again.
• After bleeding the air completely, tighten the bleed
valves.
TORQUE: 5.4 N·m (0.6 kgf·m, 4.0 lbf·ft)
Fill the reservoir to the upper level line with only Pro
Honda DOT 4 brake fluid from a sealed container.
Remove the bolt [1] and reservoir then install the
diaphragm [2], set plate [3] and reservoir cap [4] to the
reservoir.
Install the reservoir and tighten the bolt securely.

[4]

Clean up any spilled brake fluid with soapy water.
Install the following:
– front fender B, both fender covers, and front fender
A
– rear fender A
[1]

[2]/[3]

CHECK THE REPAIR
Confirm that all bleed valves are tight and there are no
leaks.
Check the pedal brake operation.

IDENTIFICATION
After you have completed the entire repair procedure,
apply a punch mark on the rear master cylinder lower
mounting tab as shown.
Install the right engine side cover.

14

PUNCH MARK