How To Service The Front Brake Master Cylinder On Your 2009 – 2010 Honda CRF450R
The Tools You Will Need Are:
- 12mm Socket
- 10mm Socket
- 8mm Socket
- Small Pick
- Stiff Brush
- Long Nose Snap Ring Pliers
- Torque Wrench
- Fine Grit Emery Paper
- Shop Towels
The Parts You Will Need Are:
This front master cylinder rebuild should cost around $25 and take approximately 30 minutes to complete.
- I recommend opening the Service & Torque Specs in a new tab for easy reference.
- If you need parts and tools, make sure to buy them on Amazon!
- Pictures with captions are after the steps below.
- Brake fluid will damage everything, so keep your shop towels ready!
- If you need any help don’t hesitate to ask!
Front Master Cylinder Removal
- Loosen and remove the banjo bolt, and wrap the end in a shop towel.
- Loosen and remove the 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.
Clean And Inspect
- Wipe every part inside and out with fresh brake fluid and a shop towel.
- If you need to scrub anything, make sure you use a nonmetallic brush.
- Inspect every component for noticeable damage.
- If you find any rough spots, gently sand it down with fine-grit emery paper. I always give the pivot bolt and the pushrod a once over to be safe.
- Measure the inside diameter of the cylinder bore and the outside diameter of the piston.
- The cylinder bore should be no Greater than 11.05 mm, and the piston should be no LESS than 10.84 mm.
- If your cylinder bore and piston are out of spec, they need to be replaced.
New Brake 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.
- 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.
- Start your assembly with the piston. Install the piston cups with the large side facing in.
- Take your time with the cups; if they are damaged during install, your brakes will not work.
- Install the new piston spring.
- Coat the master cylinder bore with brake fluid, and install the piston past the first cup.
- Install the piston in a twisting motion to avoid rolling the cups.
- Place the piston washer and spring clip on the piston.
- When installing the spring clip, ball up a piece of shop towel and place it in the pushrod, then push the piston down with a screwdriver to make room for the snap ring pliers.
- This is the hardest part of assembly because you almost need three hands, and too many things are in too small of a space.
- 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.
- To make sure the clip is in the groove, use your pick to rotate it. If it moves, it’s seated.
- Install the new boot on the pushrod. Pull the boot up and grease the pushrod, then place the pushrod in the piston.
- Gently push the boot down into the bore.
- Align the knocker arm with the pushrod, and install the brake lever spring, followed by the pivot bolt.
- Carefully pull the boot up into the groove on the knocker arm.
- Install the diaphragm and reservoir cap.
Front Master Cylinder Installation
- 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.
- Banjo Bolt – 25 ft-lbs
- Mounting Bolt – 7 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!
- Service Specification
- Clutch Replacement
- Fuel System Service
- Engine Top End
- Front Suspension & Steering
- Rear Suspension
- Wheels & Tires
- External Shift Linkage