Keihin Sudco PWK 38mm Carburetor™

Keihin PWK 38mm Carburetor Fitment Guide

Motorcycle Fitment & Replacement Guide

Looking for a replacement Keihin PWK 38mm carburetor? This guide covers some of the most common dirt bike, motocross, enduro and ATV applications associated with the PWK 38mm carburetor family.

A PWK 38mm is a popular performance carburetor for 2-stroke engines because of its strong throttle response, excellent airflow and broad tuning range. However, not every 38mm PWK carburetor is dimensionally identical. Spigot dimensions, carburetor body length, airboot diameter, throttle cable, choke configuration, vent routing and jetting can vary.

Common PWK 38mm Applications

Direct Replacement vs. Conversion Fitment

There is an important difference between a motorcycle that originally used a PWK 38mm carburetor and a motorcycle that can be converted to a PWK 38mm.

Direct / Factory PWK Applications

These motorcycles are among the strongest candidates when matching a PWK 38mm carburetor to the original carburetor family:

• Honda CR125R — 1999–2000
• Honda CR250R — 1999–2000
• Kawasaki KX250 — 1998–2007
• Kawasaki KX500 — 1988–2004
• Suzuki RM250 — 2003–2008
• KTM 250 SX / EXC / MXC — 1999–2006
• KTM 300 SX / EXC / MXC — 1999–2006
• KTM 380 SX / EXC / MXC — 1999–2002

Common PWK 38mm Conversion Applications

A number of motorcycles and ATVs are frequently fitted with a PWK 38mm as an aftermarket upgrade or replacement, even when the exact motorcycle did not originally leave the factory with that particular PWK carburetor.

• Yamaha YZ250
• Yamaha YFZ350 / Banshee
• Honda TRX250R
• Honda ATC250R
• Suzuki LT250R
• Suzuki LT500R
• Kawasaki KX500

For these applications, do not assume a universal bolt-on fit. Confirm the dimensions of the replacement carburetor against the original before ordering.

What You Should Check Before Ordering

1. Engine-Side Spigot

Measure the outside diameter of the carburetor where it enters the intake boot.

The replacement carburetor must match the intake-manifold or reed-cage boot dimensions, or an appropriate adapter/manifold must be available.

2. Airbox-Side Diameter

Measure the inside diameter of the airbox boot.

A carburetor can have the correct 38mm bore but still have an airbox connection that is too large or too small for your motorcycle.

3. Carburetor Body Length

PWK carburetors are available in different body configurations and lengths.

Compare the distance between the engine-side spigot and airbox-side inlet to make sure the replacement will fit without putting excessive stress on either rubber boot.

4. Throttle Cable

Check the throttle-cable connection and cable length.

Some installations may require the original cable, a different cable, or an adapter depending on the PWK version.

5. Choke / Starting Circuit

Verify the location and style of the choke or starting-enrichment mechanism.

Clearance around the fuel tank and frame can be an issue on some motorcycles.

6. Fuel Line and Vent Connections

Compare the fuel inlet location and overflow/vent fittings with the original carburetor.

Make sure all vent hoses can be routed correctly and away from the exhaust and other hot components.

7. Jetting

Jetting is not universal.

A carburetor that physically fits a motorcycle may require different main jets, pilot jets, needles or air-screw settings.

Jetting depends on:

• Engine displacement
• Exhaust system
• Reed system
• Air filter and airbox configuration
• Engine modifications
• Elevation
• Temperature
• Humidity
• Fuel
• Riding conditions

Always verify air/fuel mixture and tune the carburetor for the specific motorcycle.

Important KX500 Note

Kawasaki KX500 fitment deserves special attention because carburetor specifications can vary by year and reference. Some catalogs identify the KX500 application as PWK 38, while other references identify later OEM carburetors as 39mm.

For a KX500, verify the carburetor casting number and physical dimensions before ordering rather than relying on the 38mm designation alone.

Important Yamaha YZ250 Note

The YZ250 is commonly listed as a PWK 38mm conversion application. However, the factory carburetor specification changed over the model's production history, and many YZ250 models used Mikuni carburetors rather than a factory PWK 38.

Therefore, a PWK 38mm for a YZ250 should be considered a conversion/replacement application, not automatically a factory direct replacement for every year.

Yamaha YFZ350 / Banshee

The Yamaha YFZ350 / Banshee is a popular application for aftermarket PWK carburetor conversions and upgrades.

Because the Banshee uses a twin-cylinder 2-stroke engine and is commonly modified for increased performance, carburetor selection and jetting can vary significantly depending on the engine setup.

When installing a PWK 38mm on a Yamaha YFZ350 / Banshee, verify intake and airbox dimensions, throttle-cable configuration, fuel connections and the intended intake/manifold setup before installation.

Installation & Tuning Recommendation

Before installing your new PWK 38mm carburetor:

1. Compare the new carburetor with the original.
2. Confirm intake-side and airbox-side diameters.
3. Confirm carburetor body length.
4. Confirm throttle-cable compatibility.
5. Confirm choke clearance.
6. Connect and correctly route all fuel and vent hoses.
7. Start with appropriate baseline jetting.
8. Warm the engine completely.
9. Check idle and throttle response.
10. Perform final jetting adjustments under actual riding conditions.

Fitment Disclaimer

This guide is intended as a reference for selecting a Keihin PWK 38mm-style carburetor. Motorcycle manufacturers may use different carburetor specifications during a model's production run, and aftermarket PWK carburetors can vary in body dimensions and fittings.

Always verify your original carburetor dimensions, OEM part number and mounting configuration before ordering. A 38mm bore alone does not guarantee bolt-on compatibility.

For modified engines, race bikes and performance applications, professional carburetor setup and jetting is recommended.