Carburetor Diaphragm | Honda CB350 / CL350 / SL350 K0
Replacement rubber diaphragm for the Keihin CV (Constant Velocity) carburetors fitted to Honda CB350 K0–K5, CL350 K0–K5, and SL350 K0 twins. This diaphragm installs directly on your existing vacuum piston slide — you do not need to purchase a complete slide assembly.
Sold individually. Each bike uses two carburetors, so you will need to order two diaphragms to service one motorcycle.
Why You Need This
The rubber diaphragm inside each Keihin CV carburetor operates the vacuum piston slide that controls airflow through the venturi. After decades of use, the original diaphragm is often cracked, torn, or riddled with pinholes. The most common symptom of a failed diaphragm is a bike that idles fine but bogs or hesitates when you open the throttle — the vacuum leak prevents the slide from lifting properly.
Our replacement diaphragm is a direct substitute for the OEM part, allowing you to replace just the diaphragm without replacing the entire slide.
Specifications
| Replaces OEM | 16022-287-024 |
|---|
| Fits Models | CB350 K0–K5 (1968–1973), CL350 K0–K5 (1968–1973), SL350 K0 (1969–1970) |
|---|
| Quantity | Sold individually — order two per bike |
|---|
| Carburetor Type | Keihin CV (Constant Velocity) |
|---|
Installation
Installation takes roughly 5–10 minutes per slide. Our how-to video below walks through the full process:
- Remove the old diaphragm: Cut through the metal retaining ring on the 350 slide using wire dikes or tin snips. The 350 retaining ring is thicker than the 360 version, so take care not to nick the top edge of the slide where the new diaphragm will seal.
- Clean the groove: The slide has a groove approximately 1/4-inch wide where the diaphragm seats. Remove all old rubber, corrosion, and debris. Use sandpaper or a Scotch-Brite pad if needed.
- Install the new diaphragm: Work the diaphragm onto the slide like putting a tire on a rim — seat the bead into the groove all the way around. The numbers printed on the diaphragm face up, and the bead faces down into the groove.
- Secure with superglue: Peel back the diaphragm edge slightly and apply one small drop of superglue, then another drop 180 degrees opposite. Let the glue dry before reassembly.
- Orient the slide correctly: When dropping the slide back into the carburetor body, the two vent holes on the bottom of the slide must face toward the choke (air cleaner side).
Apply a light coat of gasket sealer on the edge of the diaphragm covers when reinstalling them. This helps prevent vacuum leaks at the cover seal.
Frequently Asked Questions
Will this fit a CB360?
No. The CB350 and CB360 use different diameter diaphragms — they are not interchangeable. If you have a CB360, CL360, or CJ360, you need the CB360 Carburetor Diaphragm instead.
How do I know if my diaphragm needs replacing?
Remove the diaphragm cover and spring from each carburetor, then gently stretch the diaphragm under a bright light. Look for pinholes, tears, cracks, or areas where the rubber has become stiff and brittle. If the diaphragm is still pliable with no visible damage, it can be reused. If it is cracked, crumbling, or has any holes, replace it.
What tools do I need for the installation?
Wire dikes or tin snips (for cutting the retaining ring), needle-nose pliers, a small screwdriver (for removing the jet needle), superglue, and optionally sandpaper or a Scotch-Brite pad for cleaning the slide groove.
Do I need to remove the carburetors from the bike?
Yes. The slide and diaphragm are accessed from the top of each carburetor body, so the carbs need to be off the bike and the diaphragm covers removed to access the slides.
You Might Also Need
Last updated: March 2026
