Keihin Carb Diagram: Find Parts and Read Callouts

Official Keihin carb diagrams: choose the right reference

Astemo's Keihin tuning and repair parts index provides drawings for aftermarket carburetors. These are useful references, but they do not establish fitment for every original-equipment Keihin.

For a carburetor originally supplied on a motorcycle or ATV, start with the exact vehicle's year-and-model OEM parts fiche. If the carburetor has been swapped, identify the installed unit before relying on the bike's original listing.

FCR-MX is part of the FCR design family. Its separate reference matters because a related name does not make every drawing or component interchangeable.

Exploded view, parts fiche or service manual?

An exploded view separates components visually so you can follow their relationships. A parts fiche connects an illustration to descriptions, part numbers and application information. A service manual supplies the inspection, adjustment and repair procedures.

Use the drawing to identify the component and the manual to determine how to work on it. Callout order and drawn spacing are not a disassembly sequence, torque specification or adjustment setting.

How to read an FCR-MX diagram callout

Open the FCR-MX PDF above. Find the component in the illustration, follow its numbered callout, then read the row with that number in the parts list. These three entries show why the description matters:

Callouts 32 and 90 identify separate screws. Asking for “the adjustment screw” leaves room for confusion; including the description and listed number makes the request specific.

The slow-jet entry introduces another issue: xxx is a placeholder. It is not a complete order number. The diagram directs readers to additional tuning-parts information for jetting components.

These numbers belong to this reference. Confirm them against your carburetor's application and the supplier's current listing before ordering, especially when an OEM fiche uses a different numbering system.

Callout number, part number and jet size are different

A callout number locates an item within a drawing. A part number identifies a listed component. A jet size specifies its calibration within the appropriate jet series. Keep all three separate in your notes.

Keihin's official jet list gives a concrete example: N424-21050 identifies size 50 in the N424-21 series. That is an explanation of the numbering system, not a recommendation to install a size 50 jet in your bike.

Record the series and size together. A size alone does not identify the required jet design. Preserve the full needle code, part-number suffixes and any application notes as well.

A vehicle parts fiche may list an original jet size or optional sizes. Those entries help identify available parts; they do not determine the correct calibration for an engine with different intake, exhaust, fuel or operating conditions.

What if the drawing does not match your carburetor?

First check the reference's scope, then the carburetor's full identification. A family name and bore size may leave more than one version in play. The official PWK28 sheet, for example, includes a specific identification-code note that changes which main-jet and holder references apply.

Read footnotes and the correct model column before concluding that a part is missing. An assembly may be listed as one item even though it contains several pieces. An unavailable entry or an omitted component is not permission to substitute the nearest-looking part.

If the mismatch remains, collect clear photos of both sides, the top, bowl and identification markings. Note the bike's year and model, known carburetor swaps and aftermarket components. Leave unreadable characters marked as unknown, and have a supplier or carburetor specialist help establish the match.

Turn the diagram into an accurate parts order

Before buying, put the identification and parts information in one place:

1. Carburetor: full markings, variant and the vehicle it is installed on.
2. Reference: diagram title, applicable model column and callout number.
3. Component: description, complete part number, and jet series and size where relevant.
4. Purchase details: quantity needed, whether the listing supplies an assembly or individual part, and any current replacement number.

For supported FCR-MX applications, the Tokyomods Complete Keihin FCR-MX Carb Rebuild Kit includes listed seals, an accelerator-pump diaphragm and service hardware. The rebuild kit with billet slide plate is another FCR-MX option.

Compare each kit's fitment and contents with the work your carburetor needs. A diagram's component list describes the carburetor; it is not a packing list for a rebuild kit. Jets and other hard parts may need to be selected separately.

Common Keihin carb diagram questions

Can I order a part using only its callout number?

Include the exact diagram or application when discussing a callout with a supplier. “Part 32” alone does not identify a component across different drawings.

Does the diagram show everything I can take apart?

No. The manufacturer references include warnings about removing components that are not shown. Follow the appropriate service information and get specialist help when the intended repair goes beyond it.

Can a diagram tell me why the bike runs poorly?

It can help locate a component for inspection. Diagnosing the problem still requires the bike's symptoms, mechanical condition and application-specific checks. Finding a jet on a drawing does not prove that changing it will fix the issue.