KOSO KSR 28mm PERFORMANCE CARBURETOR

Semi-Flat D-Shaped Slide • 4-Stroke Performance Carb • DA928300

Upgrade your fuel system with the KOSO KSR 28mm Performance Carburetor, designed for riders and builders looking for improved throttle response, increased fuel-flow capability, and more precise tuning than a basic stock-style carburetor.

The KSR features KOSO's semi-flat D-shaped throttle slide, which is designed to increase fuel flow for better throttle reaction. This design also helps reduce incomplete combustion and improve combustion efficiency when the carburetor is properly tuned.

The 28mm KSR is an excellent choice for many performance 4-stroke scooter, GY6, ATV, go-kart, and buggy applications, particularly engines that have been modified with big-bore kits, performance heads, cams, intake systems, or exhaust upgrades.

PRODUCT SPECIFICATIONS

• Brand: KOSO

• Series: KSR

• KOSO Part Number: DA928300

• Carburetor Size: 28mm

• Engine Type: 4-Stroke Only

• Throttle Valve: Semi-Flat D-Shaped Slide

• Air Filter Side Outside Diameter: 50mm

• Intake Manifold Side Outside Diameter: 35mm

• Main Jet: #100

• Slow / Pilot Jet: #40

• Power Jet: #30

• Jet Needle: J

• Needle Position: Position 3

• Air Adjustment Screw Baseline: 1-1/2 Turns

PLEASE NOTE: Factory jetting should be considered a starting point. Final jetting will depend on your engine and modifications.

WHY CHOOSE THE KOSO KSR?

The KSR isn't simply another stock replacement carburetor.

KOSO designed the KSR around a semi-flat D-shaped throttle slide that changes the way air and fuel are delivered as the throttle is opened.

When properly installed and tuned, the KSR design can provide:

• Faster throttle response

• Improved throttle reaction

• Increased fuel-flow capability

• Better air/fuel control

• Improved combustion efficiency

• Better support for modified engines

• Precise tuning through jets and needle adjustment

• Improved performance potential compared with restrictive stock carburetor setups

SEMI-FLAT D-SHAPED SLIDE

One of the most important features of the KOSO KSR is its specially designed semi-flat D-shaped throttle slide.

The design is intended to increase fuel flow and provide quicker throttle reaction compared with conventional carburetor designs.

For performance applications, this means the carburetor can react quickly to throttle input while supplying the additional air/fuel mixture demanded by a modified engine.

This makes the KSR particularly useful on engines equipped with:

• Big-bore cylinder kits

• Performance cylinder heads

• Big-valve heads

• Performance camshafts

• Ported cylinder heads

• Performance intake manifolds

• High-flow air filters

• Performance exhaust systems

GREAT CHOICE FOR PERFORMANCE GY6 BUILDS

The 28mm KSR can be an excellent carburetor choice for many GY6 performance combinations.

Common applications can include:

GY6 125cc / 150cc

Useful where a larger performance carburetor is appropriate, particularly when combined with intake, cylinder-head, camshaft, or exhaust modifications.

155cc PERFORMANCE BUILDS

A good option for engines where increased displacement and performance modifications require additional airflow.

171cc BIG BORE BUILDS

The 28mm size is well suited to many 171cc performance combinations using upgraded heads, cams, intake systems, and exhausts.

180cc PERFORMANCE BUILDS

Can also be used on larger GY6 builds depending on cylinder-head flow, camshaft, intake, exhaust, compression, and desired engine characteristics.

COMMON VEHICLE TYPES

Depending on the engine and intake configuration, the KSR 28mm can be used with many:

• GY6 Scooters

• Chinese Scooters

• Performance Scooters

• ATVs

• Go-Karts

• Buggies

• Custom 4-Stroke Builds

FITMENT IS NOT DETERMINED BY ENGINE SIZE ALONE. PLEASE VERIFY YOUR CONNECTION SIZES BEFORE ORDERING.

IMPORTANT – 28mm DOES NOT MEAN 28mm CONNECTION SIZE

The advertised 28mm measurement refers to the nominal carburetor bore size.

It does NOT mean that the outside of the carburetor measures 28mm.

AIR FILTER CONNECTION:

50mm Outside Diameter

INTAKE MANIFOLD CONNECTION:

35mm Outside Diameter

Please measure your existing components before ordering.

This is especially important when using aftermarket intake manifolds and air filters.

FACTORY JETTING

The KOSO KSR 28mm comes configured with:

Main Jet — #100

Slow / Pilot Jet — #40

Power Jet — #30

Jet Needle — J

Needle Position — Position 3

Air Adjustment Screw — 1-1/2 Turns Baseline

CARBURETOR TUNING MAY BE REQUIRED

Performance carburetors are designed to be tuned to the specific engine.

The factory jetting is a starting point and is not guaranteed to be the correct final jetting for your application.

Required jetting can change significantly depending on:

• Engine displacement

• Cylinder bore

• Compression ratio

• Cylinder head

• Valve size

• Camshaft

• Intake manifold

• Air filter

• Exhaust system

• Elevation

• Temperature

• Other engine modifications

Proper air/fuel tuning is important for both performance and engine reliability.

KOSO KSR VS. STOCK CV-STYLE CARBURETOR

A standard CV-style GY6 carburetor is primarily designed around smooth operation, fuel economy, and everyday drivability.

The KOSO KSR is designed with performance tuning in mind.

Its semi-flat D-shaped slide and adjustable fuel system allow a performance engine builder to tune the carburetor around the engine's airflow requirements.

For modified engines, this can provide:

Sharper throttle response

Better fuel delivery

Increased tuning capability

Better support for higher-flowing engine combinations

Improved performance potential

IDEAL FOR BIG-BORE & PERFORMANCE ENGINES

Installing a larger cylinder, performance cylinder head, camshaft, intake, or exhaust can increase the amount of air an engine is capable of moving.

At a certain point, the original carburetor can become a restriction.

A properly sized and tuned 28mm performance carburetor can help provide the additional airflow and fuel delivery needed to take advantage of those engine modifications.

The KOSO KSR is an excellent choice for builders looking to move beyond a basic stock carburetor.

IMPORTANT FITMENT INFORMATION

THIS IS A PERFORMANCE CARBURETOR AND IS NOT GUARANTEED TO BE A DIRECT BOLT-ON REPLACEMENT FOR EVERY VEHICLE.

Before ordering, please verify:

• 35mm Intake Manifold Connection

• 50mm Air Filter Connection

• Throttle cable compatibility

• Choke/enricher configuration

• Fuel line configuration

• Available installation clearance

• Your engine is a 4-stroke application

An aftermarket intake manifold, air filter, throttle cable, jets, or other components may be required depending on your particular vehicle.

IMPORTANT

FOR 4-STROKE ENGINES ONLY

The KOSO KSR carburetor is designed for 4-stroke applications.

It should not be purchased solely based on vehicle brand, engine displacement, or appearance.

PLEASE COMPARE THE SPECIFICATIONS AND CONNECTION DIMENSIONS WITH YOUR EXISTING SETUP BEFORE ORDERING.

PACKAGE INCLUDES

1 x KOSO KSR 28mm Performance Carburetor

KOSO KSR 28mm

PERFORMANCE AIR/FUEL DELIVERY • SEMI-FLAT D-SHAPED SLIDE • BUILT FOR SERIOUS CVT & 4-STROKE PERFORMANCE