Gasket Kit (Overhaul) | Honda CB550K / CB550F

Overhaul Gasket Kit | Honda CB550K / CB550F

It started with an oil leak from somewhere — and now the whole engine is on the bench. This is the most comprehensive gasket kit on the market for the CB550 four: 30 gasket types and 70 individual pieces covering a true top-to-bottom rebuild. Every paper gasket, rubber O-ring, and exhaust gasket that comes off when the engine comes apart is in this kit.

Why You Need This

Always replace gaskets, O-rings, and cotter pins with new ones whenever the engine is reassembled. Paper gaskets compress against the mating surface during the first install — pulling them off and refitting them produces a poor seal even if they look intact. O-rings take a set and won't return. Reusing them after a teardown invites the same leak that drove you to teardown in the first place.

The Overhaul Kit covers the full engine: exhaust flanges, head gasket, cylinder base, cylinder sleeve bases, clutch cover, points cover, stator cover, valve cover, breather, oil pan, starter cover, intake runners (4 O-rings to the head), valve guide underside seals (8), valve stem seals (8), rocker shaft end covers, tappet covers, dowel pin seals, cam chain tensioner bolt sealing washer, all the oil-pump-area gaskets and O-rings, dipstick, drain bolt, tach drive housing, and clutch cover adjuster screw. If you have the case halves apart, this kit is what gets the bike back together sealed.

While you have the engine open, consider our CB550 Oil Seal Kit for the engine seals (different parts — no overlap with this gasket kit), our Honda Bond 4 Gasket Sealer for the rare joint that calls for sealant, and our Valve Spring Compressor Tool to check valves against service limits while the top end is apart.

Specifications

Note — Does NOT Fit CB500K (1971–1973): Honda's CB500K is a different engine from the CB550. The two share the four-cylinder layout but the gasket dimensions and OEM numbers differ on most parts. CMC does not stock a CB500K gasket kit — sourcing those gaskets is a used-only / eBay project. If you have a 1971–1973 CB500K, this kit will NOT cover your engine.

Note — Paper Oil Filter (NOT Centrifugal): The CB550 family uses a paper-element oil filter (housing + center bolt + spring + element) on the bottom of the engine — fundamentally different from the centrifugal rotor used in the CB175/200/350/360/450 SOHC and DOHC twins. Letter B2 in this kit is the Oil Drain Bolt sealing washer; the filter element and housing O-rings are separate parts. Pick those up at the same time so the engine has a fresh filter on first start.

Note — Oil Choice: Use SAE 10W-40 or 15W-40 100% mineral only. The CB550 has a wet clutch sharing oil with the engine. Modern semi-synthetic and full-synthetic oils contain friction modifiers that cause clutch slip. As of late 2023, Shell Rotella T4, Chevron Delo 400, and Mobil Delvac 1300 reformulated to semi-synthetic and now cause clutch slippage in these engines. Add 2 oz of zinc (ZDDP) additive per US quart with every oil change — a CB550 oil change uses more than one bottle of additive.

What's in the Kit

30 gasket types, 70 individual pieces:

Installation

Difficulty: Advanced — this kit is for a full top-to-bottom engine teardown and reassembly. If you are only changing the oil, this is overkill.

Service intervals (per CMC, for routine work, not overhaul):

• Engine oil: every 1,500 miles / 2,400 km
• Paper oil filter element: every 3,000 miles / 5,000 km (every other oil change)

Notes for the rebuild:

1. Surface preparation matters more than anything else. Use a razor blade to scrape every mating surface clean, removing all traces of old gasket material and any silicone that was used along the way. Once the surfaces are physically clean, wipe with acetone to remove residual oil and adhesive.
2. Apply gaskets dry or with a thin layer of light sealer like Gaskacinch. A thin film of white lithium grease on the new paper gaskets makes them release cleanly at the next service. Do NOT use RTV silicone. Excess silicone breaks loose into the oil galley and blocks passages.
3. Always use new gaskets, O-rings, and cotter pins on every reassembly. That is why this kit exists.
4. Head reassembly: Install the cylinder base gasket, two dowel pins, and two O-rings on the upper crankcase. Blow compressed air through the dowel pin hole before installing to confirm it is not clogged.
5. Cylinder head cover torque: Twelve 6 mm screws + six 6 mm bolts. Tighten to 0.8–1.2 kg-m (5.78–8.67 ft-lbs) in a cross pattern. The torque difference across the head must not exceed 0.2 kg-m.
6. Drain plug torque: 25.3–28.9 ft-lbs. Oil filter housing torque: 19.5–23.8 ft-lbs — do not over-tighten the filter housing or it cracks.
7. Refill: 3.0 L / 3.2 US qt for CB550K0–K2 and CB550F; 3.2 L / 3.4 US qt for CB550K3 / K4. Use SAE 10W-40 or 15W-40 100% mineral oil + 2 oz zinc per US quart.

Our CB550 oil change walkthrough covers the drain plug, filter housing, refill quantity, and oil grade — the procedures that put Letters B2 and the paper filter back together at the end of a rebuild. For broader rebuild context see our CB550 Repair Overview video.

Frequently Asked Questions

Will this kit fit a 1971–1973 CB500K?

No. Honda's CB500K (1971–1973) is a different engine from the CB550 — the gasket sizes and OEM numbers do not interchange. CMC does not stock a CB500K gasket kit; you will need to source those gaskets used or off eBay. The CB550K (1974+) is the bike this kit is built for.

Will this kit fit my CB550F?

Yes. The CB550F Super Sport (1975–1977) shares the same engine and gasket set as the CB550K. Letter M (Valve Guide underside seals, qty 8) applies to both the K and F — the CB550 head uses valve guide oil seals on all eight valves.

What's different between CB550K0–K2 and CB550K3 / K4?

The engine internals and gasket set are the same across all years — this kit fits K0 through K4. The carbs change at K3 (use the K3/K4 carb rebuild kit, not the K0–K2 kit), and oil capacity goes up slightly: 3.0 L for K0–K2 + F vs 3.2 L for K3 / K4. Use the higher number for K3 / K4 only.

Does this kit include the oil filter element?

No. The paper filter element is a separate part — pick one up at the same time. Letter B2 in this kit is the drain bolt sealing washer; Letter S is the cam chain tensioner bolt sealing washer. The actual filter element and the cam chain tensioner assembly are not gasket-kit items.

Do I really need to replace every gasket if some look OK?

Yes. Always use new gaskets, O-rings, and cotter pins on every reassembly. Paper compresses against the mating surface during the first install; O-rings take a set. Reusing them after a teardown is what brings an oil leak back the next month.

My CB550 starts hard-shifting after the engine warms up — is it my oil?

Likely yes. The CB550 has a wet clutch sharing the engine oil. Modern semi-synthetic and full-synthetic motor oils contain friction modifiers that cause the clutch plates to slip. Drain whatever is in there, refill with 100% mineral SAE 10W-40 (or 15W-40 diesel-truck mineral), add 2 oz of zinc additive per quart, and the shifting feel usually returns within a tank or two. As of late 2023, Shell Rotella T4, Chevron Delo 400, and Mobil Delvac 1300 reformulated to semi-synthetic and now cause this issue.

You Might Also Need

• CB550 Oil Seal Kit — engine oil seals (separate from gaskets; no overlap with this kit)
• Honda Bond 4 Gasket Sealer — for the rare joint that calls for sealant (most use this kit dry or with Gaskacinch)
• Valve Spring Compressor Tool — check valves against service limits while the head is off
• Cam Chain Tensioner Kit — the tensioner assembly itself (Letter S in this kit is only the sealing bolt washer)
• Cam Chain — if you have the head off, inspect and replace if at service limit
• Oil Filter w/ O-Rings — the paper filter element + housing O-rings
• Ignition Rebuild Kit — points + condensers + mounting hardware while the points cover (Letter E) is off
• Carb Rebuild Kit (K0–K2) — for CB550K0–K2 + CB550F
• Carb Rebuild Kit (K3–K4) — for CB550K3 + CB550K4 (different carbs than earlier years)
• Clutch Rebuild Kit — if Letter D Clutch Cover is off, rebuild the clutch at the same time
• Zinc ZDDP Oil Additive — 2 oz per US quart, every oil change (a CB550 oil change uses more than one bottle per service)
• Anti-Seize Lubricant — for cover bolts on reinstall

Last updated: May 2026