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Aftermarket Honda CRF250R Cylinder Heads — Performance-Grade Supply for Race Teams and Engine Builders

Aftermarket Honda CRF250R Cylinder Heads — Performance-Grade Supply for Race Teams and Engine Builders

The Honda CRF250R is a different category of cylinder head order from a commuter motorcycle. We are not supplying replacement parts to a fleet of rebuilders here — we are supplying high-spec castings to performance brands, motocross engine builders, racing teams, and high-end aftermarket distributors. Honda's quarter-liter motocross flagship has gone through two distinct engine generations since 2004: the Unicam SOHC four-valve era (2004-2017) and the current DOHC era (2018-present). We produce cylinder heads for both. Bare castings, CNC-machined raw heads, fully assembled heads with titanium intake valves and Inconel-coated exhaust valves — your choice. Lower MOQs apply to this category (from 100 pieces). 17 years of mass production experience, ISO 9001 certified, 100% pressure-tested on every unit shipped.

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Technical Specifications: CRF250R Cylinder Heads

The CRF250R cylinder head specification depends on which engine era you are sourcing for. The Unicam SOHC platform (2004-2017) is fundamentally different from the DOHC platform Honda introduced in 2018. Different valve count actuation, different bore/stroke geometry, different valve sizes, different cam drive — these are not the same head with cosmetic revisions, they are two separate cylinder head architectures sharing a model name. We maintain separate tooling and CMM reference data for both.

SpecificationUnicam Era (2004-2017)DOHC Era (2018-Present)
Cam ConfigurationUnicam SOHC — single camshaft directly actuates 2 intake valves; cam exhaust lobe drives 2 exhaust valves via forked roller rocker armDOHC — dual overhead camshafts with finger-follower rocker design
Valve Count4-valve (2 intake / 2 exhaust)4-valve (2 intake / 2 exhaust)
Bore × Stroke (Early)78mm × 52.2mm (2004-2009, 12.5:1 to 12.9:1)—
Bore × Stroke (Late)76.8mm × 53.8mm (2010-2017, 13.2:1)79.0mm × 50.9mm (over-bore short-stroke design)
Compression Ratio12.5:1 to 13.2:113.9:1
Rev Ceiling (OEM)~13,500 rpm14,400 rpm (900 rpm increase over Unicam)
Intake Valve Size30.5mm (early Unicam used 31mm)33mm — larger intakes for higher airflow
Intake Valve MaterialTitanium with surface coatingTitanium
Exhaust Valve Size25-26mm26mm
Exhaust Valve MaterialHigh-temperature steel with Inconel alloy at valve neck for heat resistanceHigh-temperature steel
Valve Angle (Included)21.5°20.5° (narrower for higher compression)
Valve Lift (Intake / Exhaust)9.2mm / 8.4mm10.5mm / 9.5mm
Throttle BodyCarbureted (2004-2009) / PGM-FI 46mm (2010-2017)PGM-FI 44mm with 60° angled injector for denser fuel charge
Head Cover MaterialMagnesium (factory weight-reduction feature)Magnesium
Cylinder LinerNikasil coatingNikasil coating
CoolingLiquid-cooledLiquid-cooled (radiator area increased 6% from 2025)
Our Casting MaterialA356 aluminum (JIS AC4CH equivalent), T6 heat treatedA356 aluminum (JIS AC4CH equivalent), T6 heat treated
Deck Flatness Tolerance≤ 0.015mm (race-spec, tighter than commuter heads)≤ 0.015mm (race-spec)
Valve Seat Concentricity≤ 0.015mm (race-spec)≤ 0.015mm (race-spec)


Key Sourcing Information at a Glance

ParameterDetail
Product TypeAftermarket Honda CRF250R cylinder heads — bare castings, CNC-machined raw, or fully assembled with valvetrain. Both Unicam (2004-2017) and DOHC (2018+) platforms in production.
MOQPerformance category MOQ from 100 pieces per SKU (lower than commuter platforms because of higher unit value and smaller batch demand). Sample orders of 20-50 pieces accepted for race team qualification.
Lead Time45-60 days for stock variants. 75-90 days for race-spec ported heads with custom porting, oversized valve seats, or modified combustion chamber geometry.
Engine CompatibilityHonda CRF250R 2004-2017 (Unicam SOHC platform — separate sub-tooling for early 78mm-bore vs late 76.8mm-bore variants) and Honda CRF250R 2018-current (DOHC platform). Heads from the two eras are not interchangeable.
MaterialA356 aluminum alloy (JIS AC4CH / ZL101A equivalent), T6 heat treated. LM25 alloy available on request for high-load race applications.
Casting MethodLow-pressure die casting (LPDC) standard for CRF250R heads — the complex water jacket geometry and tight valve seat pocket spacing require LPDC's controlled metal fill. Gravity casting available for non-race applications.
Quality Verification100% high-pressure leak testing on every unit. CMM dimensional verification on deck flatness, valve seat concentricity, and (for Unicam variants) rocker shaft bore alignment. Spectrometer-verified material composition. Race-spec heads include valve seat angle inspection report.
Assembled Head OptionsTitanium intake valves (standard), Inconel-coated exhaust valves (Unicam-era spec), DLC-coated titanium valves (race-spec upgrade), oversized racing valve sets available on request.
Custom Modification OptionsPort matching, hand-polished intake and exhaust ports (Works Edition equivalent), modified combustion chamber volumes, high-compression variants up to 14.5:1, oversized valve seat installation, valve guide replacement with bronze or aluminum-bronze.
PackagingIndividual foam-padded export boxes for race-spec heads, batch cartons for standard production. Generation-coded labels (Unicam vs DOHC) on every unit.
Shipping TermsFOB Ningbo / Shanghai, CIF, or DDP. Export experience to North American MX market (Long Beach, Vancouver), European MX scene (Rotterdam, Hamburg, Genoa), Australian (Melbourne, Sydney), and Japanese (Yokohama) markets.
Documentation ProvidedMaterial composition certificate, CMM inspection report with race-spec tolerances, leak test pass record, T6 heat treatment temperature/time log, batch traceability documentation, ISO 9001 certificate.


The Unicam-to-DOHC Transition — A 14-Year Design Story

Honda's CRF250R cylinder head architecture changed completely in 2018. Understanding why this happened, and what it means for sourcing, is the difference between a competent supplier and one that gets the order wrong. The Unicam Era (2004-2017): Honda's Bet on SOHC at Race Speeds When Honda launched the CRF250R in 2004, conventional engineering wisdom held that rocker-arm valvetrains were unsuited for engine speeds above 10,000 rpm. Honda's response was the Unicam — a single overhead camshaft driving four valves through a hybrid layout: the cam directly actuates the two titanium intake valves, while the cam's exhaust lobe operates a forked, low-friction roller rocker arm that drives both steel exhaust valves through Inconel-alloy necks. The result was a cylinder head that revved past 13,000 rpm with a SOHC architecture lighter and more compact than any contemporary DOHC design. The narrow included valve angle (21.5°) flattened the combustion chamber, which let Honda run high compression while maintaining flame propagation. Magnesium head cover, magnesium clutch cover, magnesium ACG cover — every gram counted. Honda used the Unicam architecture on the CRF250R for 14 model years. The 2018 Reset: Why Honda Switched to DOHC By 2017, the CRF250R was losing the 250cc motocross class. Competitors running DOHC architectures (Yamaha YZ250F, Kawasaki KX250, Suzuki RM-Z250) were producing more peak power and higher revs. Honda's response in 2018 was a clean-sheet redesign — DOHC, dual exhaust port (a first for the CRF250R), larger 79mm bore with shorter 50.9mm stroke, 13.9:1 compression, and a rev ceiling raised to 14,400 rpm. The finger-follower rocker design replaced the Unicam's roller rocker. Titanium intake valves grew from 30.5mm to 33mm. The included valve angle narrowed from 21.5° to 20.5°. Why the 450R Kept Unicam and the 250R Did Not An interesting engineering footnote: Honda kept the Unicam architecture on the CRF450R even after switching the 250R to DOHC. The reason comes down to where in the rev range each engine makes useful power. The 450R produces peak torque and useful output below 11,000 rpm, where the Unicam's compact dimensions and low center of gravity are competitive advantages. The 250R needs to make competitive power at 13,000-14,000 rpm, where DOHC's direct-acting valvetrain gives a cleaner cam profile and higher rev ceiling. The 250R is now the only CRF model running DOHC; everything else in the Honda four-stroke off-road lineup remains Unicam.

Aftermarket Honda CRF250R Cylinder Heads — Performance-Grade Supply for Race Teams and Engine Builders

Who We Supply

For performance Cylinder Head Brands

Companies producing complete performance head packages — porting, valve upgrades, high-compression conversions, race-prepared assemblies sold to MX teams and serious privateers. We supply CNC-machined raw heads as the starting platform, with controlled valve seat pocket geometry that allows downstream porting and custom valve seat installation. Batch sizes typically 200-500 pieces per SKU per quarter. Material certificates, casting porosity inspection reports, and X-ray analysis available on request for race-application heads.


For motocross Engine Builders and Race Teams

Independent MX engine builders who serve regional race series, plus factory and privateer race team mechanics. Small batches (20-100 pieces) of race-spec assembled heads, often with custom modifications — modified combustion chamber volumes, hand-polished ports, oversized valve seat installations for racing valves up to 35mm intake. Lead times of 75-90 days for fully custom builds. Direct technical communication with our engineering team for porting specifications.


For high-End Aftermarket Distributors

Distributors serving the North American, European, and Australian MX aftermarket. Bulk replacement heads for shops handling top-end rebuilds across the 2004-current CRF250R installed base. We ship with generation-coded SKU labels (early Unicam / late Unicam / DOHC) so that distributors do not cross-ship between the three head architectures. MOQ from 100 pieces per SKU, with most distributors running quarterly consolidated orders covering multiple generations.


For OEM Brands and Private-Label Manufacturers

Long-term supply contracts with capacity reservation. For private-label brands building their own performance head line, we accept proprietary CAD data (STEP/IGES) and execute strict Build-to-Print manufacturing with full PPAP-equivalent documentation. Common scope includes custom water jacket geometry, modified intake port profiles tuned for specific injector spray patterns, and combustion chamber redesigns for compression ratios above the OEM


Frequently Asked Questions

What is your minimum order quantity for CRF250R cylinder heads?

Performance category MOQ from 100 pieces per SKU, lower than our commuter platforms. We accept sample qualification orders of 20-50 pieces for race teams and performance brands before bulk commitment. For long-term OEM contracts or private-label brand partnerships, MOQ structured around annual volume forecast. Race teams ordering hand-modified heads sometimes work with us on single-batch orders of 10-20 pieces with project pricing.

Which CRF250R generations do you produce heads for?

Both eras. Early Unicam (2004-2009, 78mm × 52.2mm bore × stroke), late Unicam (2010-2017, 76.8mm × 53.8mm), and DOHC (2018-current, 79.0mm × 50.9mm). We maintain separate tooling and CMM reference data for each. When you order, specify the model year and we will confirm fitment.

Can you supply heads with titanium valves pre-installed?

Yes. Fully assembled heads ship with OEM-spec titanium intake valves and steel exhaust valves with Inconel coating at the valve neck (for Unicam-era heads matching original Honda specification). For race-application heads we can also install CrN DLC PVD-coated titanium valves and oversized racing valve sets. Specify the valve grade and size with your inquiry.

Do you offer port-matched or hand-polished cylinder heads?

Yes. We produce Works Edition-equivalent heads with hand-polished intake and exhaust ports for race teams and high-end performance brands. Port matching can be done to specific intake manifold or exhaust header dimensions provided by the customer. Lead time for port-matched heads is 75-90 days. Specify port flow targets, intake manifold dimensions, and exhaust header dimensions with your inquiry.

What custom modifications can you make to CRF250R cylinder heads?

Common race modifications: combustion chamber volume adjustment for compression ratios up to 14.5:1, oversized valve seat installation for racing valves up to 35mm intake / 28mm exhaust, modified valve seat angles (3-angle and 5-angle cuts), hand-polished ports, port matching to specific intake/exhaust hardware, valve guide replacement with aluminum-bronze for high-RPM applications. Specify target performance characteristics in your inquiry — our engineering team can usually confirm feasibility within 48 hours.

Why is the casting material A356 and not a higher-grade alloy?

A356 (T6 heat treated) is the OEM Honda specification for the CRF250R cylinder head. Its silicon content gives thermal conductivity matched to the engine's combustion chamber thermal load, and T6 heat treatment provides the hardness and dimensional stability needed for race operation. For ultra-high-load applications (sustained 14,000+ rpm dyno work or factory-team development), we offer LM25 alloy as an upgrade — slightly higher tensile strength at the cost of marginally reduced thermal conductivity. Specify the application and we will recommend the appropriate alloy.

Do you provide X-ray inspection or other non-destructive testing?

Yes. For race-application heads (custom modifications, performance brand orders, OEM private-label) we add X-ray inspection on the combustion chamber wall thickness and water jacket integrity. This is standard on race-spec batches. For commuter-grade replacement orders, the standard quality verification (100% leak test, CMM, visual inspection) is what we provide unless you specifically request X-ray.

What is your export experience for MX-market customers?

Major MX-aftermarket destinations: North America (Long Beach, Oakland, Vancouver), Europe (Rotterdam, Hamburg, Genoa, Antwerp), Australia (Melbourne, Sydney), Japan (Yokohama, Kobe), Latin America (Santos, Veracruz). We support FOB, CIF, and DDP terms. For race teams traveling to international rounds, we can ship to event-specific addresses with expedited documentation.

Can you reverse-engineer a Honda OEM cylinder head from an intact sample?

Yes. For obsolete CRF250R variants (particularly early Unicam heads from 2004-2007 where original tooling is unavailable elsewhere) we work from intact OEM samples. Laser scanning with Hexagon CMM equipment, parametric model reconstruction, double-shrinkage compensation calculations for new tooling, and casting simulation before mold cutting. Lead time for new tooling is 75-90 days. Send sample photos and dimensions to start the qualification process.

What is the price difference between bare casting, machined raw, and fully assembled heads?

Pricing varies significantly. Bare castings are the lowest cost — heat-treated and ready for your own CNC machining. CNC-machined raw heads add machining cost (typically 40-60% above bare casting). Fully assembled heads with titanium intake valves and Inconel-coated exhaust valves add the valvetrain component cost on top (typically another 80-120% above machined raw, depending on valve specification). Race-spec hand-modified heads carry a separate project quote based on the specific modifications requested.

Why Performance Brands and Race Teams Source CRF250R Cylinder Heads From Feiya

• Race-spec tolerances as standard — ≤0.015mm deck flatness and valve seat concentricity on every unit, with ±0.010mm rocker shaft alignment on Unicam heads. CMM-verified individually.

• Both Unicam and DOHC platforms in production — we maintain separate tooling and CMM reference data for all three CRF250R head architectures (early Unicam, late Unicam, DOHC). No platform shortcuts.

• LPDC standard for race castings — low-pressure die casting on our 26 LPDC machines ensures void-free combustion chamber walls and water jacket integrity. X-ray inspection available for race-application orders.

• Direct engineering consultation — race teams and performance brands work directly with our engineering team for porting specifications, custom valve seat sizing, and combustion chamber modifications. No layers of middlemen.

• 17 years of cylinder head production — 17,000+ m² facility, 5,000+ tons annual aluminum casting capacity, 125+ CNC machining centers, 26 LPDC machines. OEM partner to publicly listed motorcycle manufacturers.

Get a Quote for Your CRF250R Cylinder Head Requirements

Send the generation (early Unicam 2004-2009 / late Unicam 2010-2017 / DOHC 2018+), application (replacement, performance brand product, race team, OEM private-label), target volume, and any custom modification requirements. For race-team orders, include intended use case (regional series, national series, factory development), target compression ratio, and any specific valve seat configurations. For performance brands building product lines, send STEP/IGES drawings and intended market positioning. Engineering team responds within 24 hours.