How To Service The Rear Brake Master Cylinder On Your 2009 – 2010 Honda CRF450R
The Tools You Will Need Are:
- 12mm Socket
- 7mm Socket
- 12mm Wrench
- 10mm Wrench
- 8mm Wrench
- 8mm Hex
- 5mm Hex
- Small Pick
- Stiff Brush
- Long Nose Snap Ring Pliers
- Torque Wrench
- Shop Towels
The Parts You Will Need Are:
- ’09-’10 Honda CRF450r Rear Master Cylinder Rebuild Kit – (Link to Amazon)
- Dot 4 Brake Fluid
- Rubber Grease – (Link to Amazon)
This rear master cylinder rebuild should cost around $25 and take about 30 minutes to complete. If you don’t have your rebuild kit yet, you can get the one I am using on Amazon!
- 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!
Rear Master Cylinder Removal
- Start by unbolting the brake lever, and removing the brake lever spring.
- Loosen the banjo bolt while the master cylinder is still mounted.
- Remove the mounting bolts, followed by the banjo bolt.
- Make sure to wrap the end of the brake line with a paper towel.
Rear Master Cylinder Disassembly
- Completely disassemble the master cylinder.
- Undo the brake lever clevis lock nut, and set the lever assembly aside.
- The nut by the boot is part of the pushrod, so don’t try to remove it. It’s there to adjust the brake lever after installation.
Related: Now that you have your brake system rebuilt, you’ll need to install fresh brake pads.
Clean And Inspect
- Scrub every part inside and out with brake cleaner and a shop towel.
- If you need to scrub anything, make sure you use a non-metallic brush.
- Inspect every component for damage or uneven wear.
- If you find any rough spots, gently sand them down with fine-grit emery paper.
- Measure the inside diameter of the cylinder bore and the outside diameter of the piston.
- The cylinder bore should be no Greater than 9.575mm, and the piston should be no LESS than 9.465mm.
- If your cylinder bore and piston are out of spec, they need to be replaced.
New Rear Master Cylinder Parts
- Before assembly, take stock of your new parts.
- I am installing an All Balls Rear Master Cylinder Rebuild Kit that includes a new pushrod boot, banjo bolt seals washers, piston cups, spring clip and piston spring.
- Make sure to match the old parts with the new parts, so you don’t throw away something you need unintentionally.
- Soak your new piston cups in fresh brake fluid for about 15 minutes before assembly.
Rear Master Cylinder Assembly
- Start your assembly with the piston. Install the piston cups with the large side facing the spring end.
- Take your time with the cups; if they are damaged during install, your brakes won’t work.
- Install the 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.
- To install the pushrod, start by holding the cylinder body with your left hand.
- Apply a layer of rubber grease to the pushrod, then position the pushrod and spring clip.
- Firmly press the pushrod down with your left thumb, and clip the pushrod into place.
- To make sure the clip is in the groove, use your pick to rotate it. If it moves, it’s seated.
- Apply some rubber grease to the inside of the new boot, and slip it over the pushrod.
- Push the boot into place with the round side of your 8mm wrench, and make sure the top of the boot seats in the groove past the nut.
- Wipe off any excess grease.
- Install the diaphragm and reservoir cap.
Related: Red rubber grease works great for brake pad pins, but it also makes tube installs way too easy!
Rear Master Cylinder Installation
- Install the banjo bolt with the new seal washers, and make sure the shank rests on the tab.
- Install the master cylinder mounting bolts.
- Install the brake lever and attach the return spring. After your rebuild, make sure to bleed the rear brake system!
Rear Master Cylinder Torque Specs
- Mounting Bolts – 10 ft-lbs
- Banjo Bolt – 25 ft-lbs
- Pivot Bolt – 27 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