2009-2010 Honda CRF450r – Front Master Cylinder Service

 How To Service The Front Brake Master Cylinder On Your 2009 – 2010 Honda CRF450r.

2009 - 2010 Honda CRF450r - Front Master Cylinder Service FeaturedThe Tools You Will Need Are:

  • 12mm Socket
  • 10mm Socket
  • 8mm Socket
  • Screwdriver
  • Small Pick
  • Stiff Brush
  • Long Nose Snap Ring Pliers
  • Calipers
  • Torque Wrench
  • Fine Grit Emery Paper
  • Shop Towels

The Parts You Will Need Are:

  • ’09-’10 Honda CRF450r Front Master Cylinder Rebuild Kit
  • Dot 4 Brake Fluid
  • Rubber Grease

You Can Get Parts And Tools Through Our Partner Links HERE!

This front master cylinder rebuild should cost around $25 and take approximately 30 minutes to complete.

Brake fluid will damage almost everything it touches, so make sure you have your shop towels ready!

Related: 2009-2010 Honda CRF450r – Bleeding Brake System

Click Here To Open Brake Specs In A New Window


(Click to Enlarge)
Loosen and remove the banjo bolt, and wrap the end in a shop towel. Remove Banjo Bolt Wrap Brake Line
Loosen and remove the mounting bolts.Remove Mounting Bolts


Completely disassemble the master cylinder.Disassemble The Cylinder
Be careful when removing the snap ring, the piston is under pressure and will jump out at you.Pull Piston
Clean every part inside and out with fresh brake fluid and a shop towel.2009-2010 Honda DRF450r - Front Master Cylinder - Clean
If you need to scrub anything, make sure you use a nonmetallic brush.Be Careful!
Inspect every component for noticeable damage.2009-2010 Honda DRF450r - Front Master Cylinder - Inspect
If you find any rough spots, gently sand it down with fine grit emery paper. I always give the pivot bolt and the push rod a once over just to be safe.Sand Push Rod
Measure the inside diameter of the cylinder bore and the outside diameter of the piston.Measure Piston
The cylinder bore should be no Greater than 11.05mm, and the piston should be no LESS than 10.84mm.Measure Bore
If your cylinder bore and piston are out of spec, they need to be replaced.Be Careful!


Related: 2009-2010 Honda CRF450r – Front Caliper Service

New Parts:

Before assembly, take stock of your new parts.

I am installing an All Balls rebuild kit that includes a new piston spring, pushrod boot, piston cups, spring clip, piston washer, and banjo bolt seal washers.New Parts Make sure to match the old parts with the new ones, so you don’t accidentally throw away something you need.

Soak your new piston cups in fresh brake fluid for 15 minutes before assembly.Soak New Cups

(Click to Enlarge)
Start your assembly with the piston. Install the piston cups with the large side facing in.2009-2010 Honda DRF450r - Front Master Cylinder - Assemble Piston
Take your time with the cups; if they are damaged during install, your brakes will not work.Be Careful!
Install the new piston spring.Install Spring
Coat the master cylinder bore with brake fluid, and install the piston past the first cup.Install Piston Into Bore
Install the piston in a twisting motion to avoid rolling the cups.Be Careful!
Place the piston washer and spring clip on the piston.Place Piston Washer And Spring Clip
When installing the spring clip, ball up a piece of shop towel and place it in the push rod, then push the piston down with a screwdriver to make room for the snap ring pliers.Use Screwdriver To Press Piston Down
This is the hardest part of assembly because you almost need three hands, and too many things are in too small of a space.Be Careful!
I find it easier to compress the spring clip before I push the piston down, that way the spring clip will stay level.

But be patient, and you will get it.

Install Spring Clip
To make sure the clip is in the groove, use your pick to rotate it. If it moves, it’s seated.Rotate Clip
Install the new boot on the push rod. Pull the boot up and grease the push rod, then place the push rod in the piston.Grease Pushrod
Gently push the boot down into the bore.Install Pushrod
Align the knocker arm with the push rod, and install the brake lever spring, followed by the pivot bolt.Install Lever
Carefully pull the boot up into the groove on the knocker arm.Pull Boot Onto Knocker Arm
Install the diaphragm and reservoir cap.Install Diaphragm And Reservoir Cap
Install the master cylinder mounting bolts hand right. Install the banjo bolt with the new seal washers, and make sure the shank rests on the tab.Install And Torque Banjo Bolt
Torque Specs:
Banjo Bolt25 ft-lbs
Mounting Bolt7 ft-lbs

Related: 2009-2010 Honda CRF450r – Rear Caliper Service

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