Honda CL450 / CB450 / CB500T Gasket Kit (Service)
Valve covers are off. Points cover is off. Carbs are coming off. The CB450 family is a DOHC parallel twin — service intervals come up fast, and every cover that moves takes a gasket with it. This is the middle tier of three CB450 family gasket kits, with all 10 gasket types (16 pieces) for routine valve adjustment, ignition timing, intake reseal, and left-side service work.
Why You Need This
The Service kit is the middle tier between Oil Change (#4019, A–F) and Overhaul (#4035, A–V). Choose this kit for work that goes beyond an oil change but stops short of pulling the cylinders — valve adjustment (Letter I, four valve cover gaskets disturbed), ignition timing service (Letter H, points cover), carb reseal (Letter G, intake manifold gaskets), or stator/shifter work (Letter J, left crankcase cover). Letters A–F carry over from the Oil Change tier so the kit also handles routine right-side oil and filter clean work.
The CB450 valve clearance comes up at 1,500 miles — CMC's recommended interval — and every adjustment removes the four small valve adjuster covers. Reusing the old gaskets is the fast path to a slow weep down the cooling fins after the first heat cycle. This kit replaces every paper and rubber surface disturbed during a routine Service.
Specifications
| Spec | Detail |
|---|
| Fits Models | CB450 K0 (1965–1967), K1 (1968), K2 (1969), K3 (1970), K4 (1971), K5 (1972), K6 (1973), K7 (1974); CL450 K0 (1967), K1 (1968), K2 (1969), K3 (1970), K4 (1971), K5 (1972–1973), K6 (1974); CB500T (1975–1976) |
| Replaces OEM Parts | 16229-283-306, 16229-283-010, 30391-283-306, 30391-283-010, 12393-283-306, 12393-283-010, 12316-283-306, 12316-283-310, 11395-283-306, 11395-283-000, 91301-426-010, 91301-393-000, 91309-286-000, 91312-PC6-003, 91305-283-000, 91355-415-000, 91307-283-000, 91304-HB3-003, 91302-943-003, 91302-200-000, 11394-292-306, 11394-292-010, 11394-292-000, 11691-283-306, 11691-283-000 |
| Sold As | Set (10 gasket types, 16 individual pieces — Letters A through J). Custom-made in the U.S.A. |
Note — the kit ships with 4 valve cover gaskets (Letter I), not 2. The CB450 family has two main valve covers (one each side), but each side also has a metal breather baffle that needs its own gasket. So a complete reseal uses 4 gaskets total. Some early K0 engines may only need 3 if a baffle is missing on one side — the spare goes in your toolbox for next time.
Note — this kit covers Service-tier work only. If you're pulling the cylinder head, head gasket, valve stem seals, or splitting the cases, you need the #4035 Overhaul Gasket Kit (A–V). The Service kit (#4064) does not include the head gasket, valve stem seals, or cylinder base gasket.
Model-Specific Notes
- CB450 K0 "Black Bomber" (1965–1967) — gaskets fit identically across all K-suffix CB450 years. The K0's wiring is different from later models, but the gasket kit is the same.
- CL450 Scrambler = K0 (1967) through K6 (1974). CL450 K5 was produced and sold across both 1972 and 1973 model years — either year is the K5.
- CB500T (1975–1976) is the bored-out evolution of the CB450 DOHC twin (498cc vs 444cc). Same gasket footprint, same kit.
- Does not fit CB500K or CB550K/F. Those are inline-four-cylinder bikes, entirely different engine architecture. "CB500" alone is ambiguous — check whether your bike is a CB500T (twin, this kit fits) or CB500K (four, this kit does NOT fit).
- Does not fit CB350 / CB360 / CB175 / CB200 / CB550K / CB550F / CB750. Each is a different engine architecture with different gasket sizes.
What's in the Kit
This Service kit includes everything from the Oil Change kit (Letters A–F) plus 4 more gasket types (G–J) that get touched during deeper service: intake manifolds, points cover, the four valve adjuster covers, and the left crankcase cover.
Honda CB450 / CL450 / CB500T Gasket Kit Comparison
| Kit | Letter | Gasket | Qty |
|---|
#4019
Oil Change Gasket Kit
(Includes Gaskets A–F) | A | Stator Rotor Cover Bolt O-Rings | 3 |
|---|
| B | Oil Rotor O-Ring | 1 |
| C | Oil Rotor Cover O-Ring Small | 1 |
| D | Oil Filter Cover O-Ring | 1 |
| E | Right Crankcase Cover Gasket | 1 |
| F | Stator Rotor Cover Gasket | 1 |
#4064
Service Gasket Kit
(Includes Gaskets A–J) | G | Intake Manifold Gaskets | 2 |
|---|
| H | Points Cover Gasket | 1 |
| I | Valve Cover Gasket | 4 |
| J | Left Crankcase Cover Gasket | 1 |
#4035
Overhaul Gasket Kit
(Includes Gaskets A–W) | K | Cylinder Base Gasket | 1 |
|---|
| L | Camshaft End Cover Gasket (Behind Points) | 1 |
| M | Camshaft End Cover Gasket | 3 |
| N | Cam Tensioner Gasket | 1 |
| O | Exhaust Gaskets | 2 |
| P | Head Gasket | 1 |
| Q | Top Cam Chain Roller Shaft Sealing O-Ring | 1 |
| R | Alignment Dowel Seals | 2 |
| S | Cylinder Base O-Rings | 2 |
| T | Valve Guide Base O-Rings | 4 |
| U | Rocker Shaft O-Rings | 4 |
| V | Dipstick O-Ring | 1 |
| W | Valve Stem Seals | 4 |
Installation
Difficulty: Intermediate
Tools needed: JIS Phillips driver (or upgrade to Upper Allen Bolt Kit for valve covers + points cover + cam end covers), 0.004" feeler gauge (for the overshoot valve-adjustment method), anti-seize, light white grease for sealing surfaces, single-edge razor blade, acetone.
- Valve adjustment (Letter I, four covers). CMC recommends a 0.08 mm (0.003 in) valve clearance — looser than the factory 0.03 mm / 0.0012 in spec to prevent cam-lobe wear at the tight setting. Use the overshoot method: set with a 0.004" feeler, then back off — "tight 4 = loose 3." Remove the four valve adjuster covers and replace each gasket on reassembly.
- Cam chain adjustment. Cam chain comes up alongside valve adjustment at the 1,500 mile service. With the stator cover off (Letter F), bring the engine to 90° past TDC compression on the left cylinder using the custom index mark, then loosen the tensioner adjuster and re-tighten.
- Ignition timing service (Letter H). Pull the points cover — clean and inspect the contact faces, set the gap, and time both cylinders against the "LF" mark for the left cylinder and the "F" mark for the right. Replace the points cover gasket on reassembly.
- Intake manifold reseal (Letter G). To replace the two paper intake manifold gaskets, remove the carbs as an assembly. Reseal with new gaskets and torque the manifold bolts evenly — an air leak at the manifold causes lean idle and erratic carb behavior.
- Left crankcase cover work (Letter J). The left cover houses the generator and starting clutch. Drain oil before removing — oil sits behind this cover. Disconnect the neutral lead and stator wiring before pulling the cover. Replace the gasket on reassembly.
- Right crankcase / oil filter (Letters A–F). If you're also cleaning the centrifugal oil filter, the right crankcase cover comes off — remove the kick starter, footrest, and the oil filter cap. The CB450 family has a separate oil filter access on the right cover — unlike the CB360, you don't need the full side cover off just for routine oil filter clean (Letter D handles the filter cover O-ring on its own).
- Clean every surface. Use a single-edge razor and acetone. Scrape every trace of old gasket material or silicone. Apply a thin coat of white grease to the sealing surface of each gasket on reassembly — this lets you pull the covers next time without ripping the gasket. Do NOT use RTV silicone — it sheds debris into the oil galleries on these wet-clutch engines.
- Refill oil if drained. 2.8 L / 2.9 US qt of SAE 10W-40 100% mineral oil + 2 oz of Zinc ZDDP additive per quart. Avoid semi-synthetic oils — modern reformulated diesel oils (Shell Rotella T4, Chevron Delo 400, Mobil Delvac 1300, all reformulated to semi-synthetic in late 2023) cause clutch slip on CB450 wet clutches.
Installation Tip: The rubberized gasket material in this kit will hold up to three or four side-cover removals before replacement — if you store the bike well between rides and keep the cover bolts at moderate torque, you'll get multiple service cycles from one set.
Full Service-tier walkthrough — cam chain adjustment, valve adjustment, and the cover-by-cover sequence that disturbs Letters F, H, and the four valve cover gaskets (I). For carb work (Letter G), see our CB450 / CL450 Carburetor Rebuild walkthrough and the CB450 / CL450 / CB500T Carburetor Synchronization KB article for the post-reseal sync procedure.
Frequently Asked Questions
Why does this kit come with 4 valve cover gaskets when my bike only has 2 valve covers?
Both are right — you have 2 main valve covers, but each side also has a metal breather baffle that sits behind the cover with its own gasket. That's 4 gaskets total for a complete reseal. Some early K0 engines may only use 3 if one of the baffles is missing or different on your bike — if you only need 3, the spare goes in your spares bin. We've shipped this kit with 4 since launch, and it's the most common customer question on this page.
Does this fit my CB500T?
Yes. The CB500T (1975–1976) is the bored-out evolution of the CB450 DOHC twin — same engine architecture, same gasket footprint. The 498cc displacement comes from a wider cylinder bore but the gaskets stay the same.
Does this fit my CB500K, CB550K, or CB550F?
No. Those are inline-four-cylinder bikes — entirely different engine family. The "CB500" name is ambiguous: the CB500T is a DOHC parallel twin (this kit fits) and the CB500K is the four-cylinder predecessor of the CB550 (this kit does NOT fit). Check whether your bike has 2 carbs (twin) or 4 carbs (four-cylinder) if you're unsure.
What's the difference between #4019 Oil Change, #4064 Service, and #4035 Overhaul?
Three tiers, cumulative letter scope:
- #4019 Oil Change (A–F): Six gaskets and O-rings for routine oil and centrifugal filter clean — what gets disturbed when the right crankcase cover comes off.
- #4064 Service (A–J): A–F plus four more (G–J) — intake manifolds, points cover, four valve adjuster covers, and the left crankcase cover. Covers routine valve adjustment, ignition timing, and carb reseal.
- #4035 Overhaul (A–V): Everything in the Service kit plus 12 more gaskets and O-rings (K–V) that only get touched when the cylinder head or cylinders come off — head gasket, cylinder base, cylinder base O-rings, valve guide base O-rings, exhaust gaskets, cam tensioner gasket, camshaft end covers, rocker shaft O-rings, and dipstick O-ring.
How often should I adjust the valves?
Every 1,500 miles (2,400 km) — CMC's standard interval for the CB450 family. We recommend a 0.08 mm (0.003 in) valve clearance, which is looser than Honda's factory 0.03 mm spec. The tighter factory setting causes cam-lobe wear; the CMC setting is what we've used in our own shop for years. Use the overshoot method: set with a 0.004" feeler gauge, then back off — "tight 4 = loose 3."
Are valve stem seals in this kit?
No. Valve stem seals (Letter T — "Valve Guide Base O-Rings", qty 4) are in the #4035 Overhaul Gasket Kit only. If you're pulling the cylinder head, you need the Overhaul tier. Service tier is for cover-only work that doesn't disturb the head or valve guides.
Does this kit fit my CB450 K0 "Black Bomber"?
Yes. Gaskets fit identically across all CB450 K-suffix years (K0 through K7, 1965–1974). The K0 has different wiring from later models, but the gasket fitment is unchanged.
Should I upgrade the cover bolts to Allen bolts while I'm in there?
Yes — the original Phillips screws strip easily, especially after 50 years of impact-driver service. The Upper Allen Bolt Kit covers valve covers, points cover, breather, intake covers, and cam end covers — directly relevant to the work in this Service kit. The Lower Allen Bolt Kit covers the side covers and right crankcase area.
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Last updated: May 2026
