How do I strip and rebuild the carburetor on a Mazda RX-7 FB?

Rebuilding the stock Nikki 4-barrel carburetor on a first-gen RX-7 is a great project, but it requires patience and extreme organization. I would rate this task as Moderate to Hard, depending on your experience with carburetors and vacuum routing.

Here is how you should approach stripping and rebuilding the Nikki carb on your FB.

1. Source the Right Kit

Factory Mazda rebuild kits have been discontinued for a while, but aftermarket options are available. The community consensus is to use a Hygrade or Standard brand rebuild kit (often found on RockAuto), as these typically include the correct metal sealing washers ². You can also get DIY kits from rotary specialists like Mazdatrix or Atkins Rotary, but be aware that their kit components are aftermarket now, not OEM ².

2. Get the Documentation

Do not wing this teardown. Before you turn a single screw, download the factory service manual and the specific Nikki carburetor manual. You can find these digitized in the RX-7 manual archives at foxed.ca or wankel.net ³.

3. Teardown and Cleaning

Generally on a carburetor of this type, you will separate the air horn (top plate), the main body, and the throttle base.

• Take plenty of photos as you disconnect the linkages and springs.
• Remove the jets, emulsion tubes, and accelerator pump components. Keep everything organized in labeled trays so every part goes back exactly where it came from.
• Clean all metal components thoroughly with carburetor cleaner. However, do not use compressed air or harsh solvents on any rubber components or diaphragms, as it can easily damage them ³.

4. Nikki-Specific Rebuild Quirks

When reassembling, the community strongly recommends a few deviations from a standard rebuild:

• Keep the factory needle valve and seats. Do not swap in the aftermarket ones from your rebuild kit, as the factory originals are generally higher quality and more reliable ².
• Leave the floats alone. Unless you have a known float issue, it is highly recommended not to touch or attempt to adjust the floats during the rebuild ².

I don't have verified torque figures for the carburetor body screws or the exact float level measurements for your car, so don't take a number from me on it — check the factory service manual. The procedure itself is straightforward: seat the brass jets gently just until they bottom out (do not overtighten, or you will strip them), and snug the main body screws evenly in a criss-cross pattern to prevent warping the housing.

5. Reinstallation and Tuning

Once the carb is back together and on the manifold, getting it to run right usually comes down to vacuum routing and idle adjustments.

• Vacuum Leaks: The Nikki has a complex vacuum system. Pay special attention to the shutter valve and the #2 AAV hose (often called the "mystery hose" on the passenger side). This hose runs from the top rear of the AAV down to the lower rear of the intake manifold. Because it sits right next to the exhaust manifold, it is incredibly prone to splitting and causing massive vacuum leaks ⁵.
• Idle Adjustments: There are three main idle adjustment screws on these carbs. The two in the middle of the body are your air screw (large) and fuel/mixture screw (small). The throttle stop screw is on the right side and is locked in place with a 7mm nut that can be a pain to access ⁴. Adjust the air and fuel mixture screws incrementally to dial in your idle once the car is at operating temperature.