Master Cylinder | Honda CB360 / CB450 / CB500T

Description

Master Cylinder (Full Replacement) for Honda CB350G / CB360 / CB400F / CB450 / CB500T / CB500K / CB550

Direct-fit replacement master cylinder for the Honda twin and four-cylinder hydraulic front brake. 14 mm piston, matches the factory bore. Includes the brake lever. This is what you install when the original master cylinder bore is too pitted or scored to rebuild.

Why You Need This

Sometimes the master cylinder on your Honda simply cannot be rebuilt. Years of sitting in old brake fluid turn the bore into aluminum dust — the corrosion goes deeper than a hone can reach, or the bore is scored from a piston that seized. At that point a rebuild kit won’t save it, and you need a new master cylinder.

Ours comes ready to mount with the correct look and feel for your Honda. The piston is 14 mm, identical to the original factory unit, so it pairs correctly with the stock caliper bore ratio and the brake lever already has the right feel. Brake fluid attacks rubber as it ages and absorbs moisture, so any cracking, swelling, or weeping in the rubber parts means replace immediately — and when the housing is past the rubber-parts stage, this is the next step.

Specifications

Note: This master cylinder is not a perfect visual copy of the Honda factory unit — the housing shape is close but not identical. It fits and performs exactly like the original. If factory-original appearance matters for a concours restoration, rebuild the original housing with our rebuild kit instead.

Does NOT fit the CB750. The CB750 uses a different, larger master cylinder. Separate CB750-specific parts are required.

Installation

Difficulty: Beginner to Intermediate. A bolt-on replacement — no rebuild work involved. The time budget is driven by the bleed, not the swap.

Tools needed: 10 mm and 12 mm box wrenches (master cylinder clamp + banjo bolt), 8 mm box wrench for the bleeder screw, clear vinyl tubing, catch bottle, fresh DOT 3 brake fluid, nitrile gloves, rag to protect paint.

1. Protect painted surfaces near the master cylinder. Brake fluid damages paint on contact.
2. Drain the old fluid out through the caliper bleeder, then disconnect the brake hose at the master cylinder banjo fitting. Cover the open end of the hose with a rag.
3. Unclamp the old master cylinder from the handlebar and remove it.
4. Install the new master cylinder on the handlebar. Snug the clamp — don’t fully torque yet.
5. Connect the brake hose to the new master cylinder banjo fitting. Use new copper crush washers on both sides of the banjo bolt — crush washers are one-time-use.
6. Square the master cylinder body to the handlebar angle you want, then tighten the clamp.
7. Fill the reservoir with fresh DOT 3 brake fluid from a sealed container.
8. Bleed the system. The master cylinder doesn’t move much fluid per stroke — do a two-stage bleed: start with the hard line disconnected at the caliper, purge until fluid runs clear and air-free, then reconnect the line and bleed at the caliper bleeder. A speed bleeder with built-in check valve makes this significantly faster.
9. Check lever free play at the tip: 2–5 mm (0.08–0.2 in.). Firm lever = you’re done. Spongy lever = air still in the system — re-bleed.