Service Bulletin
American Honda Motor Co., Inc.

2001-2015 GL1800/A, GL1800B/BD SECONDARY MASTER CYLINDER REPLACEMENT

GL1800 #23 - REPAIR PROCEDURE

Service Bulletin
American Honda Motor Co., Inc.

SAFETY RECALL
OVERVIEW ·················································· 1-2

PEDAL BRAKE LINE FLUID FLUSHING ···· 1-9

PEDAL BRAKE LINE FLUID DRAINING ····· 1-2

PEDAL BRAKE LINE FLUID FILLING ······· 1-12

REPLACE THE REAR M ASTER CYLINDER 1-4

PEDAL BRAKE LINE AIR BLEEDING ······· 1-14

REM OVE THE FRONT WHEEL··················· 1-7

CHECK THE REPAIR ································· 1-14

REM OVE THE SECONDARY M ASTER
CYLINDER ··················································· 1-8

IDENTIFICATION ······································ 1-14

’12-’15 GL1800

GL1800B/BD

©2015 American Honda M otor Co., Inc. – All Rights Reserved
M TB 15624 (1510)

1

GL1800 #23 - REPAIR PROCEDURE
GL1800 #23 - REPAIR PROCEDURE

OVERVIEW
OBJECTIVE
This repair procedure, when properly executed, will eliminate most contaminants from the pedal brake system
prior to the installation of the secondary master cylinder (SMC) parts kit.
The procedure differs significantly from the Service Manual brake filling/bleeding sequence, as it includes a
fluid flushing procedure and the installation of a new rear master cylinder (to ensure all contaminants are
removed from the pedal brake line) before the final fluid filling and bleeding. Carefully review the complete
procedure before starting. AHM will issue Service Manual revision pages to update the Service Manual with the
new brake fluid replacement procedure.
Use only the provided Pro Honda DOT 4 brake fluid from sealed containers to ensure the quality of the
repair procedure.

PARTS, SUPPLIES, AND TOOLS
REQUIRED
In addition to common hand tools, the brake fluid replacement procedure requires the following parts, supplies
and tool:
– Master cylinder kit, second/rear (For model application, see the PARTS INFORMATION section of this
bulletin.)
P/N 06454-MCA-306 (1) or
P/N 06454-MJG-306 (1)
– Use only Pro Honda DOT 4 brake fluid (6 bottles per repair) Initially, automatically shipped separately from
the parts kit.
– Applicable Service Manual
– Commercially available brake bleeder

TRIKE CONVERSIONS or MODIFIED
BRAKES
If the vehicle is a trike conversion, or has a modified, disabled, or removed secondary master cylinder (SMC)
and the SMC is non-functional, note these facts on the R.O. and contact TechLine for further instructions.

PEDAL BRAKE LINE FLUID DRAINING
Spilling fluid can damage painted, plastic or rubber
parts. Place a shop towel over these parts whenever
the system is serviced.
• Do not mix different types of fluid. They are not compatible.
• Do not allow foreign material to enter the system when filling the reservoir.

PEDAL BRAKE LINE FLUID DRAINING
RIGHT FRONT CALIPER

SECONDARY
MASTER CYLINDER

REAR MASTER CYLINDER

DELAY
VALVE

ANTI-DIVE
PLUNGER
PCV

LEFT FRONT
CALIPER

2

REAR
CALIPER

GL1800 #23 - REPAIR PROCEDURE
Refer to the Service Manual and remove the following:

[2]

– right engine side cover
– front fender A, both fender covers, and front fender
B
– rear fender A
Support the motorcycle on its centerstand or a lift.
Remove the bolt [1] and rear master cylinder reservoir.
Remove the rear master cylinder reservoir cap [2], set
plate [3], and diaphragm [4].
Temporarily install the reservoir and tighten the bolt.
[1]

Connect a commercially available brake bleeder [1] to
the bleed valve of the pedal brake line as shown.
Loosen the bleed valve and activate the brake bleeder
until no more fluid flows out of the bleed valve.
Close the bleed valve.

Perform the fluid draining procedure at each remaining
valve of the pedal brake line in the following order:
1.
2.
3.
4.

[3]/[4]

[1]

Right front caliper:

Rear caliper:

right front caliper, lower: [1]
rear caliper, lower: [2]
anti-dive plunger: [3]
rear caliper, upper: [4]

[1]

[2]
Rear caliper:

Anti-dive plunger:

[4]
[3]

3

GL1800 #23 - REPAIR PROCEDURE

REPLACE THE REAR MASTER
CYLINDER
REMOVAL
Remove the two screws and brake light/cruise cancel
switch (’13 – ’14 GL1800B: brake light switch) assembly
[1] from the master cylinder.

[1]

Remove the two bolts [2] and right footpeg [3].

[4]

[2]

Remove the pinch bolt [4] and brake pedal [5].

When removing the
hose and oil bolt,
cover the ends of
the hoses to
prevent
contamination.

Remove the reservoir hose [1] from the master cylinder
[2].

[5]

[3]

[4]

[3]

Disconnect the brake hose by removing the oil bolt [3]
and sealing washers [4].

[2]
[2]
[1]

Unhook the spring end to remove the return spring [1]
from the frame and pivot arm [2].

[4]

[3]

Release the drive shaft joint boot [3] from the engine.
Remove the master cylinder mounting bolts [4].
Remove the pedal pivot arm from the frame while
pushing the water hose aside, then remove the master
cylinder/pivot arm assembly [5].
[5]

[2]

4

[1]

GL1800 #23 - REPAIR PROCEDURE
Remove the following from the master cylinder:

[1]

– split pin [1]
– joint pin [2]
– pivot arm [3]

[3]

[2]

CLEAN THE RESERVOIR
AND OIL BOLT
Use a wire brush if
necessary to clean
the oil bolt threads.

Thoroughly clean the reservoir [1], hose [2], and oil bolt
[3] with WATER only. DO NOT USE BRAKE
CLEANER!

[3]

[1]

Blow all components dry with compressed air.
[2]

INSTALLATION
MASTER CYLINDER

OIL BOLT

SEALING WASHERS

PIVOT ARM

BRAKE LIGHT/CRUISE CANCEL
SWITCH ASSEMBLY
RETURN SPRING
RIGHT FOOTPEG

BRAKE PEDAL

5

GL1800 #23 - REPAIR PROCEDURE
Install the pivot arm [1] into the new master cylinder
push rod joint with the joint pin [2] and a new split pin
[3].

[3]

[1]

Apply grease to the pivot shaft groove of the pivot arm
[1].

[2]

[2]

[3]

[4]

Place the master cylinder/pivot arm assembly [2] into
the frame while pushing the water hose and driveshaft
joint boot aside, then insert the pivot arm into the pivot
hole, being careful not to damage its splines.
Install the master cylinder onto the frame and tighten
the mounting bolts [3].
TORQUE: 12 N·m (1.2 kgf·m, 9 lbf·ft)
Install the joint boot [4] onto the engine.
Install the return spring [5] into the pivot arm and onto
the frame stopper pin in the direction shown.

[1]

Install the reservoir hose [1] onto the joint.

[5]
[3]

[2]

Connect the brake hose to the master cylinder with the
oil bolt [2] and new sealing washers [3], and tighten the
oil bolt.
TORQUE: 34 N·m (3.5 kgf·m, 25 lbf·ft)

[1]

Install the brake pedal [1] by aligning the slit with the
punch mark on the pivot arm.

[2]

Install the pinch bolt [2] and tighten it.
TORQUE: 27 N·m (2.8 kgf·m, 20 lbf·ft)
Align

[1]

6

GL1800 #23 - REPAIR PROCEDURE
Install the footpeg [1] and tighten the bolts [2].

[2]

TORQUE: 27 N·m (2.8 kgf·m, 20 lbf·ft)

[1]

Apply locking agent to the threads of the switch holder
screws.
Install the brake light/cruise cancel switch (’13 – ’14
GL1800B: brake light switch) assembly [1] with the
screws.
Adjust the switch position so that the brake light comes
on when pushing the brake pedal slightly and the push
rod moves 0.7 – 1.7 mm.
Tighten the switch holder screws.

[1]

TORQUE: 1.5 N·m (0.2 kgf·m, 1.1 lbf·ft)

REMOVE THE FRONT WHEEL
Refer to the Service Manual, remove the front wheel.

7

GL1800 #23 - REPAIR PROCEDURE

REMOVE THE SECONDARY MASTER
CYLINDER
REMOVAL
Remove the following:
When removing the
oil bolt, cover the
joints of the hoses
to prevent