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
| Spec | Detail |
|---|
| Replaces OEM Part Numbers | 45500-369-671, 45500-341-771, 45530-377-305, 45504-300-003, 45505-300-003, 45506-300-003, 45512-300-003, 45502-300-305, 46125-533-003, 46140-533-003, 90651-377-003, 45520-300-000, 45526-341-000, 45521-MJ6-006, 45521-300-010, 45517-MA5-671, 45517-300-003, 95701-06025-00, 95700-06025-00, 45527-300-000, 94002-06000-0S, 53175-369-003, 53170-369-003, 43513-MJ6-006, 43513-461-771, 5513-341-771, 90114-300-000 |
| Fits Models | CB350G (1973), CB360G/T (1974–1976), CB400F (1975–1977), CB450 K2–K7 (1969–1974), CB500K (1971–1973), CB500T (1975–1976), CB550K (1974–1978), CB550F (1975–1977) |
| Piston Diameter | 14 mm (matches the factory unit) |
| Brake Lever | Included |
| Brake Fluid Spec | DOT 3 |
| Lever Free Play Spec | 2–5 mm (0.08–0.2 in.) at the tip |
| Sold As | Complete master cylinder assembly with lever |
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.
- Protect painted surfaces near the master cylinder. Brake fluid damages paint on contact.
- 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.
- Unclamp the old master cylinder from the handlebar and remove it.
- Install the new master cylinder on the handlebar. Snug the clamp — don't fully torque yet.
- 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.
- Square the master cylinder body to the handlebar angle you want, then tighten the clamp.
- Fill the reservoir with fresh DOT 3 brake fluid from a sealed container.
- 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.
- 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.
Our Ultimate Guide to Rebuilding the Honda CB Hydraulic Front Brake System covers the complete front brake workflow. See Part 2 for the two-stage bleed method.
Frequently Asked Questions
Does this fit my CB750?
No. The CB750 uses a different master cylinder with a larger piston diameter — this one will not fit. Separate CB750-specific parts are required.
Does this fit my CB400F or CB350F?
Yes. The CB400F Super Sport and CB350F four-cylinder use the same Tokico master cylinder as the rest of the CB family listed above. Confirmed in our Master Cylinder KB article.
Does this fit my CB450 K2?
Yes. The CB450 K2 (1969) has the hydraulic front disc brake with the same master cylinder used through the K7. The K0 and K1 are drum-brake bikes and this part doesn't apply to them.
When should I replace the master cylinder vs rebuild it?
Replace if: the bore is deeply pitted or scored, the housing is cracked, the piston bore is out-of-round, or the clamp mounting ears are stripped. Rebuild with our rebuild kit if: the bore has only light surface corrosion that a hone will clean up, the piston is stuck but the bore is otherwise smooth, or the rubber seals are the only problem.
Is the replacement visually identical to the Honda original?
No. The housing shape is similar but not a perfect visual copy of the factory unit. It fits the same, feels the same at the lever, and uses the same brake hose / banjo / reservoir cap hardware. If factory appearance matters for a show bike or concours build, rebuild your original housing instead.
What brake fluid should I use?
DOT 3. That's the factory spec across this brake family. Don't mix DOT 3 with DOT 5 (silicone) — the two are not compatible and mixing them will damage the seals.
Does it come with the brake lever?
Yes. The brake lever is included, already fitted to the master cylinder. If you prefer an OEM-style lever appearance, our OEM-style disc brake lever is a direct swap.
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Last updated: April 2026
