Chromed Carburetor Diaphragm Cover | Honda CB350 / CL350 / SL350 K0
The chromed diaphragm covers sit right on top of your Keihin CV carburetors, in plain view whenever the tank is off. After fifty years of fuel, weather, and road grime, the originals are usually pitted, dull, or flaking. These are a direct chrome replacement — they seal the same and put the factory shine back on top of the carbs.
Sold individually. Each bike runs two carburetors, so you will need two covers to do one motorcycle.
Why You Need This
Each Keihin CV carburetor uses a chromed cover to cap the vacuum piston slide and its spring. That cover has to seal cleanly against the top of the carburetor: the coat of sealer around its edge is what keeps vacuum from leaking past, and that vacuum is what lifts the slide as you open the throttle. A fresh cover gives you a clean, unpitted sealing face — and takes the tired, corroded look off the top of the engine.
Specifications
| Finish | Chrome |
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| Fits Models | CB350 K0–K5 (1968–1973), CL350 Scrambler K0–K5 (1968–1973), SL350 K0 (1969–1970) |
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| Carburetor Type | Keihin CV (Constant Velocity) |
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| Sold As | Sold individually — order two per bike |
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Installation
Difficulty: Beginner
Mind the spring. There is a spring under the cover that pushes up on the slide, so keep a thumb on the cover as you back out the screws — it wants to pop up as the last screw comes loose. On reassembly, drop the spring in first, then set the cover over it.
Seal the cover. Run a light coat of gasket sealer around the cover's outer edge before you bolt it down — a thin, rubber-cement-style sealer, or RTV used very sparingly, works well. Let it tack up before you fit the cover. The point of the sealer is to keep the top of the carburetor from leaking vacuum.
Snug the screws evenly. A dab of anti-seize on the cover-screw threads keeps them from seizing. Start the screws catty-corner and bring them down a little at a time so the cover pulls flat.
Part 4 of our CB350 carburetor rebuild series walks through pulling the slide, inspecting the diaphragm, and resealing the cover on the way back together:
Frequently Asked Questions
Will this fit a CB360?
No. The CB360 family uses a different cover. If you have a CB360, CL360, or CJ360, you need the CB360 Chrome Diaphragm Cover instead.
How many covers do I need?
One per carburetor, so two for a complete bike. They are sold individually, so order two to do both carbs.
My cover screws are chewed up. Can I replace them?
Yes. The factory JIS screws strip easily after decades in service. Our Carburetor Allen Head Bolt Set swaps the diaphragm-cover screws for stainless allen hardware you can actually turn without rounding off.
Does the cover come with a new diaphragm?
No — the cover is sold on its own. If the rubber diaphragm underneath is torn or full of pinholes while you are in there, replace it with our CB350 Carburetor Diaphragm.
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Last updated: July 2026
