GY6 125cc / 150cc PERFORMANCE • A-BLOCK • 54mm STUD SPACING

Upgrade the breathing capability of your GY6 performance engine with the NCY Big Valve High-Flow Cylinder Head.

Designed for A-Block GY6 engines with 54mm cylinder stud spacing, this performance cylinder head features oversized intake and exhaust valves, improved port design and an enlarged combustion chamber designed to work with 61mm big-bore cylinder setups.

Increasing valve size and improving airflow can help a properly tuned big-bore engine move more air through the combustion chamber, making this an excellent cylinder head for performance GY6 builds where the stock head becomes a restriction.

NCY SKU: 1100-1254

IMPORTANT FITMENT — READ BEFORE ORDERING

A-BLOCK / 54mm STUD SPACING ONLY

This cylinder head is designed for the older/common GY6 A-Block engine configuration using approximately 54mm cylinder stud spacing.

WILL NOT FIT:

• B-Block GY6 engines with 57mm stud spacing

• K-Block engines

• QMK engines

• 161QMK engines

• Other newer large-case GY6 engines using the wider stud pattern

• 139QMB / QMB139 50cc GY6 engines

DO NOT ORDER BASED ON ENGINE DISPLACEMENT ALONE.

There are multiple versions of GY6 engines. A 150cc, 170cc or larger GY6-style engine does not automatically mean this head will fit.

MEASURE YOUR CYLINDER STUD SPACING BEFORE ORDERING.

If your engine is a 57mm B-Block or newer K-Block/QMK configuration, this cylinder head WILL NOT FIT.

BIG VALVE DESIGN

Equipped with oversized valves to increase potential airflow compared with a typical stock GY6 cylinder head.

• Intake Valve: Approx. 27.8mm

• Exhaust Valve: Approx. 22.9mm

The larger valve area is especially beneficial on big-bore engines where increased displacement requires greater intake and exhaust flow.

HIGH-FLOW PORT DESIGN

The intake and exhaust passages are designed to improve breathing for performance applications.

Potential benefits on a properly matched and tuned engine include:

• Improved cylinder filling

• Increased intake flow

• Improved exhaust flow

• Better throttle response

• Stronger performance at higher RPM

• Better support for big-bore engine combinations

Actual performance will depend on the complete engine combination, including displacement, camshaft, carburetor, intake, exhaust, ignition and CVT tuning.

DESIGNED FOR 61mm BIG-BORE BUILDS

This head is an excellent match for 61mm cylinder / big-bore combinations on compatible A-Block engines.

A 61mm bore combined with the common approximately 57.8mm GY6 stroke produces approximately 169cc–171cc, commonly marketed as a 171cc big-bore setup.

It may also be useful in other compatible performance A-Block combinations, but piston-to-valve clearance, combustion chamber clearance and component compatibility must always be verified when building a modified engine.

Brand: NCY
Product: Big Valve High-Flow Cylinder Head
Application: Performance GY6 4-Stroke Engines
Engine Block: A-Block ONLY
Cylinder Stud Spacing: Approx. 54mm
Recommended Bore: 61mm performance applications
Intake Valve Diameter: Approx. 27.8mm
Exhaust Valve Diameter: Approx. 22.9mm
Exhaust Stud / Thread Size: 8mm
Material: Aluminum Alloy
Cooling: Air-Cooled / Finned Design
Country of Origin: Taiwan
SKU: 1100-1254

CYLINDER HEAD AS SHOWN / HEAD ASSEMBLY ONLY

This listing is for the NCY cylinder head itself.

No additional engine components are included unless specifically pictured or stated in the listing.

Do not assume that a cylinder kit, piston, rings, camshaft, rocker assembly, intake manifold, carburetor, gaskets, timing components or other engine parts are included.

Compatible NCY replacement/performance valve set:

NCY High-RPM Racing Valve Set – Approx. 28mm Intake / 23mm Exhaust

Valve Set SKU: 1100-1257

Always verify valve dimensions and compatibility before purchasing replacement valves.

Designed primarily for GY6 125cc / 150cc A-Block engine families using the 54mm cylinder stud pattern, including compatible versions of:

• 152QMI – 125cc GY6

• 157QMJ – 150cc GY6

• 1P57QMJ – compatible A-Block versions

• Other GY6 A-Block engines using the same 54mm stud pattern

These engines can be found in many Chinese and Taiwanese scooters, ATVs, go-karts and buggies.

POSSIBLE VEHICLE BRANDS / APPLICATIONS

Depending on the specific engine installed:

• TaoTao

• Ice Bear

• Wolf Brand

• Bintelli

• ZNEN

• Peace Sports

• Roketa

• Jonway

• SUNL

• Tank

• Hammerhead

• TrailMaster

• Carter

• Yerf-Dog

• Various Chinese 125cc / 150cc scooters

• Various GY6-powered go-karts and buggies

• Various GY6-powered ATVs

BRAND OR MODEL NAME DOES NOT GUARANTEE FITMENT.

Manufacturers frequently used different GY6 engine versions in the same vehicle family. Verify your engine code, cylinder stud spacing and existing cylinder-head dimensions before ordering.

This distinction is extremely important when purchasing performance GY6 engine parts.

A-BLOCK

54mm stud spacing

This is the engine configuration this NCY head is designed to fit.

B-BLOCK

Approximately 57mm stud spacing

WILL NOT FIT.

K-BLOCK / QMK

Newer/larger GY6-style engine platform commonly associated with engine codes such as 161QMK and related QMK configurations.

WILL NOT FIT.

A cylinder head designed for the 54mm A-Block cannot simply be substituted onto the wider B-Block or K-Block/QMK engine.

Installing a big-valve cylinder head changes the airflow capability of the engine. Proper tuning is necessary to take advantage of the upgrade.

Depending on your engine combination, tuning may involve:

• Carburetor jetting

• Air/fuel mixture adjustment

• Larger carburetor

• Performance intake

• Performance exhaust

• Performance camshaft

• Valve adjustment

• Ignition tuning

• CVT tuning

CARBURETOR JETTING

A big-bore/high-flow engine will often require a richer fuel mixture than a stock engine.

Do not assume a specific #125 or #130 main jet is correct for every build.

Required jet size depends on the carburetor, air filter, intake, exhaust, camshaft, displacement, elevation, temperature and other modifications.

Start from a safe baseline and properly tune the air/fuel mixture for your individual engine.

Running a performance engine excessively lean can cause overheating and serious engine damage.

Increasing displacement without improving cylinder-head airflow can eventually make the stock head a restriction.

A properly matched big-valve head can allow a performance engine to:

• Move a greater volume of air

• Better support increased displacement

• Improve high-RPM breathing

• Improve throttle response

• Take better advantage of performance camshafts

• Work more effectively with larger carburetors

• Support higher-output big-bore combinations

For a 61mm A-Block GY6 performance build, the cylinder head is an important part of creating a properly matched engine combination.

BEFORE ORDERING — VERIFY THESE 3 THINGS

1. Your engine is an A-Block GY6

2. Your cylinder stud spacing is approximately 54mm

3. Your cylinder/bore and other engine components are compatible with this cylinder head

54mm A-BLOCK ONLY

NOT FOR 57mm B-BLOCK

NOT FOR K-BLOCK

NOT FOR QMK / 161QMK ENGINES

NCY PERFORMANCE

BIG VALVES • HIGH-FLOW DESIGN • 61mm BIG-BORE APPLICATION • MADE IN TAIWAN

SKU: 1100-1254

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