Carburetor Rebuild Kit | Honda CB450 / CL450 / CB500T
Varnished jets, stuck slides, and leaking float bowls are the most common reason a CB450 or CL450 won't idle or run right after sitting. This rebuild kit replaces all the wear items inside your Keihin CV carburetors with fresh jets, gaskets, seals, and a new float needle and seat.
Note: Kits are sold individually — you will need to order TWO kits to service both carbs.
Why You Need This
The Keihin CV carburetors on the Honda CB450 and CL450 are straightforward to rebuild — no rubber diaphragm, just a tight-tolerance aluminum slide and a clip-style float bowl that pops off without any screws. But after decades of sitting, the brass jets corrode, float needles wear out and leak fuel, and gaskets harden and shrink. A full rebuild with fresh internals restores proper fuel metering and eliminates the rich running, fuel overflow, and poor idle that come with aged carburetors.
Each kit includes both early and late style idle mixture screw components so you can match whichever version your carburetors use. The early style has a threaded shaft with an O-ring recessed in the head. The late style has a threaded head, smooth shaft, and uses a spring with a washer and O-ring at the bottom.
Specifications
| Spec | Detail |
|---|
| Fits Models | CB450 K0–K7 (1965–1974), CL450 K0–K6 (1967–1974), CB500T (1975–1976) |
| Fits Carburetors | Keihin CV (constant vacuum) — factory original |
| Main Jet | #130 (CB450/CL450), #145 (CB500T) |
| Pilot / Low Speed Jet | #38 |
| Secondary Jet | #38 |
| Sold As | Individual kit — order TWO per bike |
Model-Specific Notes
- CB450 K0 / CL450 K0: These models use a unique style of main jet that is not included in the kit. You will need to reuse your original K0 main jet.
- CB500T: The CB500T carburetors are nearly identical to the CB450 with the addition of a rubber anti-backfire diaphragm and a vacuum sync port. Order the CB500T version of this kit, which includes the #145 main jet, air cutoff diaphragm, diaphragm spring, and diaphragm-to-body O-rings.
What's in the Kit
CB450 / CL450 Kit Includes:
- Main Jet — #130
- Pilot / Low Speed Jet — #38
- Secondary Jet — #38
- Float Needle and Seat with sealing washer
- Main Jet Needle with set screw and collar
- Emulsifier Tube with Discharge Nozzle
- Idle Mixture Screw with Spring (early and late styles included)
- Float Bowl Gasket
- Slide Cover Gasket
- Idle Mixture Screw O-ring
- Drain Plug O-ring or Gasket
- Aluminum sealing washers
CB500T Kit Also Includes:
- #145 Main Jet
- Air Cutoff Diaphragm
- Air Cutoff Diaphragm Spring
- Air Cutoff Diaphragm to Carburetor Body O-Rings
Installation
Difficulty: Intermediate
- Remove the float bowl by sliding the retaining clip off — no screws to remove.
- Press out the float hinge pin, remove the float and float needle. Inspect the float — shake it near your ear and check for hairline cracks. If you hear fuel sloshing inside, replace the float.
- Remove the main jet, idle jet, secondary jet, and emulsifier tube. The discharge nozzle must be tapped out from the opposite side with a small round punch.
- Remove the slide cover screws and pull out the slide assembly. The jet needle is held in the slide by a small flat-head set screw.
- Remove the idle mixture screw — note whether your carb has the early or late style, and use the matching replacement from the kit.
- Clean all carburetor body passages thoroughly before reassembly.
- Reinstall the discharge nozzle (blunt side toward the bottom of the carb body), then the emulsifier tube, fresh main jet, pilot jet, and secondary jet.
- Install the new float needle seat with its sealing washer, then the float. Set float height to 20mm as measured from the gasket surface with the carburetor held vertically — the float tab should just touch the needle valve without compressing the internal spring.
- Install the new jet needle with collar into the slide, secure with the set screw, and test that the slide moves freely in the carb body with no binding.
- Seat the idle mixture screw fully, then back it out approximately 1.5 turns as a baseline starting point.
Slide binding tip: If the slide catches, try loosening and re-tightening the top cap. You can also rotate the top cap 180 degrees or swap top caps between carburetors to find the best fit. These slides run dry — do not grease them.
After rebuilding: Synchronize both carburetors on the bench before reinstalling on the motorcycle.
Our full CB450 / CL450 carburetor rebuild video walks through every step of disassembly, inspection, and reassembly — including how to identify early vs. late style idle mixture screws and how to set the float height.
Frequently Asked Questions
Do I need one kit or two to rebuild both carburetors?
You need two kits. Each kit rebuilds one carburetor, and the CB450, CL450, and CB500T all have two carburetors.
How do I know if I have early or late style carburetors?
Look at the idle mixture screw. The early style has a threaded shaft with an O-ring recessed in the head. The late style has a threaded head, a smooth shaft, and uses a spring, washer, and O-ring at the bottom. Both styles are included in every kit, so you just use the one that matches your carburetors.
Will this kit fit a CB500T?
Yes — the CB500T uses nearly identical Keihin CV carburetors with the addition of an anti-backfire diaphragm and vacuum sync port. Order the CB500T version of this kit, which includes the correct #145 main jet and the air cutoff diaphragm components.
What is the correct float height for the CB450 / CL450 / CB500T?
Honda specifies 20mm. Measure with the carburetor held vertically, from the gasket sealing surface to the top of the float, with the float tab just touching the needle valve without compressing its internal spring.
My CB450 K0 — does this kit work?
Yes, with one exception: the K0 models use a unique style of main jet that is not included in the kit. You will need to reuse your original K0 main jet. All other components in the kit are correct for the K0.
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Last updated: March 2026
