Carburetor Gasket & O-Ring Kit | Honda CB450 / CL450 / CB500T
When your CB450 or CL450 carbs just need fresh seals — not a full rebuild — this is the gasket and O-ring kit that reseals one factory Keihin carburetor. It covers the float bowl, slide cover, mixture screw, and drain plug seals so a carb that's otherwise in good shape stops weeping and holds a clean idle again.
Why You Need This
Old float-bowl gaskets shrink and leak, the mixture-screw O-rings harden and stop sealing, and a weeping drain plug makes a mess. If your carb bodies and brass are still in good shape and you just need to reseal, this kit gets you there without paying for a full rebuild kit. If the brass is chewed up or worn, step up to the full carburetor rebuild kit instead.
What's in the Kit
- Float bowl gasket
- Slide cover gasket
- Sealing washers (float needle seat and idle mixture chamber)
- Idle mixture needle O-rings (both early and late style)
- Drain plug O-ring
Specifications
| Spec | Detail |
|---|
| Fits Models | CB450 K0–K7 (1965–1974), CL450 K0–K6 (1967–1974), CB500T (1975–1976) |
| Sold As | Sold individually (one kit reseals one carburetor) |
Note: Sold individually. A CB450 / CL450 / CB500T has two carburetors, so order two kits to reseal both.
CB500T owners: this kit reseals the CB500T carbs, but it does not include the seal for the CB500T's air-cut (anti-backfire) valve diaphragm. If you're servicing that, add the CB500T air cutoff valve separately.
Model-Specific Notes — Early vs. Late Idle Mixture Screw
The 450 / 500T family used two styles of idle mixture screw, and the kit includes O-rings for both. Check which one your carb has before you install:
- Early style: threaded along the length of the body, with the O-ring seated in a groove on the screw — use the larger O-ring, and there's no seal at the tip.
- Late style: smooth body with a stepped tip and threads only at the head — uses the small O-ring at the tip plus a small metal washer. Save and re-use that washer; it carries over from your original screw and isn't in the kit.
Installation
Difficulty: Intermediate
- Pull the carbs and remove the float bowls and slide covers. Lay out the old seals so you can match the new ones as you go.
- Replace the float bowl gasket, slide cover gasket, and the sealing washers behind the float needle seat and idle mixture chamber.
- Fit the correct mixture-screw O-ring for your style (early or late), and on a late-style screw put the saved metal washer back on.
- Put a drop of light oil on the O-rings and the mixture-screw threads as you reassemble so they seat without tearing.
For the full teardown — float height, jets, and mixture-screw setup — see our carb rebuild walkthrough below.
Our CB450 / CL450 carburetor rebuild video shows where each of these gaskets and O-rings goes, including the early vs. late mixture screw and the float bowl that pops off without screws.
Frequently Asked Questions
Do I need one kit or two?
Two for a full bike. Each kit reseals one carburetor, and the CB450 / CL450 / CB500T has two, so order two kits to do the pair.
What's the leftover O-ring or washer for?
The kit includes mixture-screw O-rings for both the early and late carb styles, so you'll have the O-ring for the style you don't have left over. On a late-style screw there's also a small metal washer at the tip — that one carries over from your original screw, so re-use it rather than looking for a new one in the kit.
Will this reseal my CB500T carbs?
Yes, for the main carburetor seals. The one thing it doesn't cover is the CB500T's air-cut (anti-backfire) valve diaphragm — that's a CB500T-specific part you'd add separately if you're servicing it.
Should I get this or the full rebuild kit?
Get this gasket and O-ring kit if your carbs are clean and the brass is in good shape and you just need fresh seals. Step up to the full rebuild kit if the jets and needle-and-seat are worn or gummed up.
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Last updated: June 2026
