Keihin Sudco PWK 28mm Carburetor 016-141 / KH-900109™

Keihin PWK 28mm Carburetor Fitment Guide

Motorcycle, ATV & Small-Engine Fitment Guide

Looking for a replacement or performance upgrade for a Keihin PWK 28mm carburetor? The PWK 28 is one of the most popular small-bore flat-slide carburetors for 2-stroke motorcycles, motocross bikes, mini bikes, trials bikes, scooters and performance applications.

The PWK 28mm is commonly used on engines ranging from approximately 65cc through 150cc, with additional applications possible depending on the engine configuration and intended use. It is also frequently used as an aftermarket conversion on larger or modified engines.

Important: A 28mm bore does not automatically mean a carburetor is a direct bolt-on replacement. Always verify the intake spigot, air-filter connection, carburetor length, throttle cable, choke arrangement and other physical dimensions before ordering.

Common Keihin PWK 28mm Applications

PWK 28mm Carburetor Dimensions

A standard Keihin PWK 28mm carburetor is approximately:

• Engine-side connection: 35 mm outside diameter
• Air-filter side: 49 mm outside diameter
• Carburetor length: 83 mm
• Overall height: 147.4 mm

These dimensions are useful when determining whether a replacement PWK 28mm will physically fit your motorcycle. Aftermarket PWK-style carburetors may have different dimensions, so always compare the actual carburetor you are purchasing with the original carburetor.

Direct Replacement vs. Conversion Fitment

There is an important difference between a motorcycle that was designed around a PWK 28mm carburetor and a motorcycle that can accept a PWK 28mm as an aftermarket upgrade.

Factory / Strong PWK 28mm Applications

The following models are among the more established PWK 28mm applications:

• Honda CR85R / CR85RB
• Kawasaki KX85 / KX100
• Kawasaki KX105 / KX105R
• Yamaha YZ85
• Yamaha YZ100
• Suzuki RM80 / RM85
• Suzuki RM100
• Selected KTM small-bore applications

Kawasaki documentation identifies the KX85 and KX112 platform as using a PWK 28 semi-flat-slide carburetor, while genuine Keihin PWK28 listings specifically identify applications such as the Honda CR85 and Kawasaki KX105.

Common PWK 28mm Conversion Applications

The PWK 28mm is also frequently installed as an aftermarket performance upgrade or replacement on motorcycles and ATVs that did not originally use the exact same PWK 28 configuration.

Common conversion applications include:

• Yamaha YFZ350 / Banshee
• Yamaha YFS200 Blaster
• Yamaha DT100 / DT125
• Yamaha YZ85 / YZ100 conversions
• Honda CR80 / CR85 applications
• Suzuki RM80 / RM85 applications
• Aprilia RS50 / RX50 / SX50
• Derbi Senda / GPR 50
• Various 50cc–125cc 2-stroke applications

Yamaha YFZ350 / Banshee

The Yamaha YFZ350 / Banshee is a particularly popular aftermarket application for Keihin PWK 28mm carburetors.

Because the Banshee is a twin-cylinder 2-stroke, it normally uses two PWK 28mm carburetors when converted to a dual-PWK setup rather than a single carburetor.

Aftermarket Banshee PWK 28 kits are commonly sold as matched pairs and are designed around the Banshee's dual-carburetor configuration. Depending on the kit, the installation may use the factory intake boots or aftermarket intake components.

Important: Banshee fitment can vary depending on the intake system, throttle-cable setup, airbox configuration, engine modifications and carburetor manufacturer. Verify the complete kit contents before ordering individual carburetors.

Yamaha Blaster YFS200

The Yamaha Blaster YFS200 is another popular PWK 28mm conversion application.

A PWK 28mm can provide improved throttle response and tuning flexibility, but it is not necessarily a direct replacement for every factory connection on the Blaster.

Depending on the carburetor and installation, an air-cleaner adapter, appropriate throttle cable or other installation hardware may be required.

50cc–125cc 2-Stroke Applications

PWK 28mm carburetors are commonly used as performance upgrades on small-displacement 2-stroke motorcycles and scooters.

Examples include selected:

• Aprilia RS50
• Aprilia RX50
• Aprilia SX50
• Derbi Senda
• Derbi GPR
• Yamaha DT100
• Yamaha DT125
• Yamaha YZ80 / YZ85
• Yamaha YZ100
• Suzuki RM80 / RM85
• Other AM6- and similar-platform 50cc 2-strokes

Because many of these motorcycles were originally equipped with different carburetor brands or sizes, these should be treated as conversion applications unless the specific motorcycle and carburetor combination has been verified.

Trials Motorcycle Applications

Keihin PWK 28mm carburetors are also used on selected trials motorcycles.

For example, 2012–2013 Sherco 290 and 305 models are documented with 28mm carburetor applications, while other Sherco models may require a different intake manifold when changing carburetor size.

Always verify the intake-manifold size and throttle-cable arrangement before installing a PWK 28mm on a trials motorcycle.

What You Should Check Before Ordering

1. Engine-Side Spigot

Measure the outside diameter of the carburetor's engine-side spigot and compare it with the inside diameter of your intake boot or manifold.

A standard PWK 28mm uses approximately a 35mm engine-side outside diameter, but aftermarket carburetors may vary.

2. Airbox / Air-Filter Connection

Measure the inside diameter of your airbox boot or air-filter connection.

A standard PWK 28mm is approximately 49mm OD on the air-filter side. An adapter may be required on some motorcycles.

3. Carburetor Length

Check the distance between the engine-side and air-filter-side connections.

A carburetor that is too long or too short can make installation difficult and may put stress on the intake boot or airbox connection.

4. Throttle Cable

Verify that the throttle cable can connect correctly to the PWK slide mechanism.

Some applications use a motorcycle-specific cable, while conversion installations may require an aftermarket cable or adapter.

5. Choke / Starting Circuit

Check the location and type of the choke or starting-enrichment mechanism.

Frame, fuel-tank or bodywork clearance can vary considerably between motorcycles.

6. Fuel Inlet

Check the location and size of the fuel inlet before installation.

Make sure the fuel line can be routed without kinking and remains safely away from hot engine or exhaust components.

7. Vent and Overflow Hoses

Make sure there is adequate space for all carburetor vent and overflow hoses.

Incorrect vent routing can cause poor running or fuel-delivery problems.

Jetting Information

Jetting is not universal.

A PWK 28mm that physically fits your motorcycle may require different jetting depending on the engine and riding conditions.

A commonly published standard specification for a genuine PWK28 is:

• Main jet: #135
• Pilot / slow jet: #38
• Needle: 46-JJH
• Throttle valve: 3.5
• Float height: 19mm

These specifications are a reference starting point only and should not be considered universal jetting for every motorcycle.

Final jetting may need to be adjusted for:

• Engine displacement
• Exhaust system
• Reeds and reed cage
• Airbox configuration
• Air filter
• Porting
• Compression
• Engine modifications
• Elevation
• Temperature
• Humidity
• Fuel
• Riding conditions

Installation & Tuning Recommendation

Before installing your PWK 28mm carburetor:

1. Compare the new carburetor with the original carburetor.
2. Confirm the engine-side spigot diameter.
3. Confirm the airbox or air-filter connection diameter.
4. Confirm carburetor body length and clearance.
5. Verify throttle-cable compatibility.
6. Verify choke clearance and operation.
7. Connect and correctly route the fuel and vent hoses.
8. Start with appropriate baseline jetting.
9. Warm the engine completely before tuning.
10. Check idle quality and throttle response.
11. Perform final jetting adjustments under actual riding conditions.

Fitment Disclaimer

This guide is intended as a general reference for selecting a Keihin PWK 28mm-style carburetor. Motorcycle manufacturers may use different carburetor specifications during a model's production run, and aftermarket PWK-style carburetors can differ in dimensions, fittings and internal calibration.

A 28mm bore alone does not guarantee bolt-on compatibility.

Always verify your original carburetor dimensions, OEM part number, intake boot, airbox connection, throttle cable and mounting configuration before ordering.

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