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:

  • Front Master Cylinder Rebuild Kit
  • Dot 4 Brake Fluid
  • Rubber Grease

If you don’t have your rebuild kit yet, you can get the one I am using HERE (link to RockymountainATVMC.com).

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

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

Click Here To Open Brake Specs In A New Window

Front Master Cylinder Removal:

(Click to Enlarge)
Loosen and remove the banjo bolt, and wrap the end in a shop towel.  2009-2010 Honda DRF450r - Front Master Cylinder - Wrap Brake Line
Loosen and remove the mounting bolts.2009-2010 Honda DRF450r - Front Master Cylinder - Remove Mounting Bolts

Front Master Cylinder Disassembly:

Completely disassemble the master cylinder.
Be careful when removing the snap ring, the piston is under pressure and will jump out at you.2009-2010 Honda DRF450r - Front Master Cylinder - Pull Piston
Clean:
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 non metallic brush.Be Careful!
Inspect:
Inspect every component for obvious 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.2009-2010 Honda DRF450r - Front Master Cylinder - Sand Push Rod
Measure:
Measure the inside diameter of the cylinder bore, and the outside diameter of the piston.
The cylinder bore should be no Greater than 11.05mm and the piston should be no LESS than 10.84mm.2009-2010 Honda DRF450r - Front Master Cylinder - Measure Bore
If your cylinder bore and piston are out of spec, they need to be replaced.Be Careful!

New Parts:

Before assembly, take stock of your new parts.

I am installing an All Balls rebuild kit that includes a new piston spring, push rod boot, piston cups, spring clip, piston washer, and banjo bolt seal washers.2009-2010 Honda DRF450r - Front Master Cylinder - New PartsMake 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.2009-2010 Honda DRF450r - Front Master Cylinder - Soak New Cups

Front Master Cylinder Assembly:
(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.2009-2010 Honda DRF450r - Front Master Cylinder - Install Spring
Coat the master cylinder bore with brake fluid, and install the piston past the first cup.2009-2010 Honda DRF450r - Front Master Cylinder - 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.2009-2010 Honda DRF450r - Front Master Cylinder - 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.2009-2010 Honda DRF450r - Front Master Cylinder - Use Screwdriver To Press Piston Down
This is the hardest part of assembly because you almost need 3 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.

2009-2010 Honda DRF450r - Front Master Cylinder - Install Spring Clip
To make sure the clip is in the groove, use your pick to rotate it. If it moves, it’s seated.2009-2010 Honda DRF450r - Front Master Cylinder - 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.2009-2010 Honda DRF450r - Front Master Cylinder - Grease Pushrod
Gently push the boot down into the bore.2009-2010 Honda DRF450r - Front Master Cylinder - Install Pushrod
Align the knocker arm with the push rod, and install the brake lever spring, followed by the pivot bolt.2009-2010 Honda DRF450r - Front Master Cylinder - Install Lever
Carefully pull the boot up into the groove on the knocker arm.2009-2010 Honda DRF450r - Front Master Cylinder - Pull Boot Onto Knocker Arm
Install the diaphragm and reservoir cap.2009-2010 Honda DRF450r - Front Master Cylinder - Install Diaphragm And Reservoir Cap
Front Master Cylinder Install:
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.2009-2010 Honda DRF450r - Front Master Cylinder - Install And Torque Banjo Bolt
Torque Specs:
Banjo Bolt25 ft-lbs
Mounting Bolt7 ft-lbs

If you have any questions or anything to add, please leave them in the comments or on our FaceBook page!

Keep Your ’09-’10 CRF450r Running Right!

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