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Aftermarket Yamaha YZ85 Cylinder Heads — Bulk Supply for B2B Buyers Worldwide

Aftermarket Yamaha YZ85 Cylinder Heads — Bulk Supply for B2B Buyers Worldwide

We supply aftermarket Yamaha YZ85 cylinder heads to two-stroke engine builders, youth-motocross parts distributors, and OEM brands worldwide. The YZ85 is an 85cc liquid-cooled reed-valve two-stroke with the Yamaha Power Valve System (YPVS), so its head is a billet or cast combustion-chamber cap with a squish band, coolant jacket, and central spark-plug bore — no valvetrain. The standard YZ85 and the big-wheel YZ85LW share the same engine and head. We CNC-machine from 6061-T6 billet for the squish band, chamber volume, and sealing face, and pressure-test every unit. MOQ 500 pieces per SKU, samples accepted, ISO 9001 certified.

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Technical Specifications: Yamaha YZ85 Cylinder Heads

The YZ85 head is a small-bore two-stroke head, and small bore makes squish even more critical than on a 125. The engine is an 85cc liquid-cooled reed-valve two-stroke with YPVS, fed by a compact 28mm carburetor, and it revs hard for its size. On a head with no valvetrain, the squish band and combustion chamber are the whole job. A wide or loosely toleranced squish on a small high-revving 85 invites detonation and lost power fast, so squish has to be cut tight and profiled to the piston, with the base-gasket stack accounted for. One fitment point matters here: the standard YZ85 (17-inch front wheel) and the big-wheel YZ85LW (19-inch front) use the same engine and the same cylinder head, so a single head covers both. Our motorcycle cylinder head program covers the YZ85 from its 2002 launch onward.

SpecificationStandard Value
Engine PlatformYamaha YZ85 youth motocross two-stroke. Standard YZ85 and big-wheel YZ85LW share the same head — specify model year in RFQ.
Engine Type2-stroke, single cylinder, reed-valve induction, liquid-cooled, YPVS power valve
Displacement85cc (nominal)
Head TypeTwo-stroke combustion-chamber head — no valvetrain. Single central spark-plug bore, integrated squish band and coolant jacket.
Construction OptionsSolid billet head, or modular two-part head with a swappable chamber insert for ratio changes. Gravity-cast version offered where unit cost leads.
Material6061-T6 billet as standard — its high thermal conductivity matters on a small engine that spins to high rpm and concentrates heat in a tiny chamber. A356-T6 cast for economy tiers; 7075 on request.
Squish ClearanceCut tight to the piston and base-gasket stack. The small 85cc bore leaves little margin, so squish is set conservatively for detonation control on pump fuel.
Compression OptionsChamber volume set to your ratio, with pump-fuel and race-fuel profiles for youth-class racing and high-altitude options.
Power Valve ContextYPVS operates in the cylinder, not the head, but the chamber profile is chosen to complement the power-valve tuning. Specify your setup.
CoolingLiquid-cooled jacket sized for the small chamber; the modular two-part design routes more coolant around the chamber wall.
SealingBillet heads seal on O-rings (supplied with the head plus copper washers); cast designs use a head gasket.
Deck/Sealing Flatness≤ 0.02mm (CMM verified on every unit)
Wheel Variant FitmentStandard YZ85 (17/14) and YZ85LW big wheel (19/16) use the same head. Wheel size does not change the cylinder head.
Supply OptionsFinished billet head, cast blank, or modular head with selectable chamber insert. Private-label engraving available.
Surface FinishAs-machined, bead-blasted, or anodized (black/blue/custom) on request


Key Sourcing Information at a Glance

ParameterDetail
Product TypeAftermarket YZ85 two-stroke cylinder heads — finished billet, cast blank, or two-piece dome design. Built to fit the Yamaha YZ85 engine; this is a replacement and performance part, not an original-equipment Yamaha component.
MOQ500 pieces per SKU for standard variants. Sample orders of 50-100 pieces accepted for first-time buyers. CNC billet runs of 100-300 pieces accepted for performance brands.
Lead Time30-45 days for stock variants. 45-70 days for new billet programs, custom squish/compression specs, or two-piece dome tooling.
Model CoverageYZ85 from the 2002 launch onward, including the big-wheel YZ85LW (same head). Confirm model year so the correct casting ships.
Material6061-T6 billet (standard for performance heads) or A356-T6 cast. Material certificates provided.
Custom Spec InputsTarget compression ratio, fuel grade (pump vs race), squish clearance, base-gasket thickness, and altitude. We advise baseline gasket and squish stack on request.
Quality Verification100% pressure leak testing. CMM verification of squish band, chamber volume, and sealing face. Spectrometer-verified material. Batch records archived for 5 years.
PackagingStandard export carton, neutral packaging, or private-label cartons. Billet heads ship with O-rings and copper washers.
Shipping TermsFOB Ningbo/Shanghai, CIF, or DDP. Export experience to the US, Australia, Europe, and other youth-motocross markets.
Documentation ProvidedMaterial certificate, CMM inspection report, leak test record, batch traceability, ISO 9001 certificate, commercial invoice, packing list, certificate of origin.


How to Source the Right YZ85 Head: Wheel Variants, Squish, and Pitfalls

The YZ85 is the entry point to Yamaha's two-stroke motocross line, and sourcing its head is straightforward once two things are clear: which physical bike the buyer has, and whether the squish is cut for that engine. The 85 is small and high-strung, so squish errors punish it harder than they do a bigger engine. YZ85 vs YZ85LW Big Wheel Yamaha sells the YZ85 in two forms: the standard model with a 17-inch front and 14-inch rear wheel, and the big-wheel YZ85LW with a 19-inch front and 16-inch rear for taller young riders. The wheels differ, but the engine and the cylinder head are the same. One head covers both. Buyers sometimes assume the LW needs a different head — it does not. From 2002 Onward The liquid-cooled YZ85 launched in 2002, replacing the older air-cooled YZ80. If a buyer references a YZ80, that is an earlier, different engine with its own head. For the YZ85, confirm the model year so the correct casting and chamber detail ship. Why squish is critical on a small bore On a two-stroke there is no valve job, so the head is the squish band and chamber. A small 85cc bore is sensitive: a wide or imprecise squish causes detonation and power loss quickly, and a young rider on a high-revving engine has little margin for a head that pings. Cutting squish tight and profiling it to the piston, with the base-gasket stack accounted for, is the core of a good YZ85 head. This is the main reason a precision-machined head outperforms a loosely toleranced one. Common avoidable mistakes when buying Assuming the big-wheel LW needs a different head. It uses the same engine and head as the standard YZ85. Confusing the YZ85 with the older air-cooled YZ80. The YZ80 is a different, earlier engine. Confirm you are sourcing for the liquid-cooled 85. Ordering without the piston and gasket stack. Squish is set by head geometry plus base-gasket thickness and piston deck height. Send your piston and base-gasket spec or the squish figure is a guess. Skipping material choice. 6061 billet sheds heat better than 7075 or cast on a small high-revving engine. For racing, specify 6061-T6.

Aftermarket Yamaha YZ85 Cylinder Heads — Bulk Supply for B2B Buyers Worldwide

Who We Supply

For Two-Stroke Engine Builders

Orders supported across the standard YZ85 and big-wheel YZ85LW, which share one head (300-2,000 pieces per SKU). Builders we supply keep stock because youth motocross engines see frequent top-end service as kids ride hard and grow into bigger bikes. We machine squish and chamber volume to your target and include a CMM report on every batch. Sample qualification runs of 50-100 pieces accepted before bulk commitment.


For Youth-Motocross Distributors

Private label and neutral packaging available. We support drop-shipping to consolidation warehouses and regional hubs across North America, Europe, and Australia, where youth motocross is strongest. The YZ85 head is a steady aftermarket line because the bike is the standard entry point to two-stroke racing and the rebuild cycle is short. Distributors stocking the full Yamaha two-stroke MX range typically run quarterly consolidated shipments.


For Performance & Tuning Brands

CNC billet programs in small batches. We produce one-piece billet heads and two-piece designs with interchangeable domes for compression tuning, machined from 6061-T6 for thermal performance. Pump-fuel and race-fuel chamber profiles for youth-class racing, with squish cut to the piston. Runs of 100-300 pieces accepted for qualified performance brands. Specify compression, fuel grade, and squish target.


For OEM & Private-Label Programs

Long-term OEM and private-label supply with capacity reservation. We supply heads to listed motorcycle manufacturers under multi-year agreements and accept proprietary CAD (STEP/IGES) for build-to-print work. In-house tooling and billet programming typically take 45-70 days from approved DFM to first-article approval. Custom anodizing and engraving for brand identity supported.


Frequently Asked Questions

What is your minimum order quantity for aftermarket YZ85 cylinder heads?

Standard MOQ is 500 pieces per SKU for variants in our production library, covering the YZ85 and the big-wheel YZ85LW (same head). Sample qualification orders of 50-100 pieces are accepted for new clients, and CNC billet runs of 100-300 pieces for performance brands. Long-term OEM MOQ is structured around your annual forecast.

Does the big-wheel YZ85LW use a different cylinder head?

No. The YZ85LW big wheel differs from the standard YZ85 only in wheel size — 19-inch front and 16-inch rear versus 17 and 14. The engine and the cylinder head are identical, so one head covers both models. Buyers sometimes assume the LW needs its own head, but it does not.

Is the YZ85 head the same as the older YZ80 head?

No. The liquid-cooled YZ85 launched in 2002 and replaced the older air-cooled YZ80, which is a different, earlier engine with its own head. The 85 head does not fit a YZ80. Confirm you are sourcing for the liquid-cooled YZ85.

Why is squish clearance so important on the YZ85?

On a two-stroke there is no valve job, so head quality comes down to the squish band and chamber, and a small 85cc bore is especially sensitive. A wide or imprecise squish causes detonation and power loss quickly on a high-revving small engine. We cut squish tight and profile it to the piston, with the base-gasket stack accounted for, which is the core of a reliable, strong YZ85 head.

Do you make billet heads with adjustable compression?

Yes. We produce two-piece heads with interchangeable domes so you can change compression and chamber profile without replacing the whole head, plus one-piece billet heads cut to a fixed ratio. Pump-fuel and race-fuel profiles are available for youth-class racing. Tell us your target compression, fuel grade, and intended use.

Do I need to tell you my piston and base-gasket spec?

Yes, for performance heads it matters. Squish clearance is set by head geometry combined with your base-gasket thickness and piston deck height. Without that, a squish figure is only an estimate. Send your piston model and base-gasket thickness and we will set the squish stack correctly, and advise gasket thickness if you are unsure.

Does the YPVS power valve affect the cylinder head?

The YPVS power valve operates in the cylinder, not in the head, so it does not change the head casting. But the head's chamber profile and compression are chosen to complement the power-valve tuning, so tell us your setup and intended power character and we will recommend a matching chamber.

What material do you use, and is 6061 better than 7075 or cast?

Our standard performance material is 6061-T6 billet, which conducts heat better than 7075 and better than cast alloys — an advantage on a small, high-revving two-stroke. A356-T6 cast is available for economy tiers, and 7075 on request, though 6061 is usually the better thermal choice. All material is spectrometer-verified.

What is the typical lead time?

30-45 days for variants in our standard library, from PO confirmation to FOB-ready. 45-70 days for new billet programs, custom squish/compression specs, or two-piece dome tooling. Bulk reorders on existing programs ship within 21-30 days for established customers.

What other YZ85 engine parts do you supply besides cylinder heads?

Our primary focus is cylinder heads. We also produce engine covers and intake-related castings, and can quote cylinders and crankcase components for the YZ85 platform on request. For distributors building a full YZ85 top-end range, list the parts and volumes in your RFQ for a consolidated quote.

Why B2B Buyers Source YZ85 Cylinder Heads From Feiya

• 17 years of motorcycle cylinder head production — with tooling and CMM reference data for the YZ85, including the big-wheel YZ85LW that shares the same head.

• Squish cut tight for a small bore — squish band and chamber volume CMM-verified on every unit and profiled to the piston, the dimension that decides detonation control and power on an 85.

• 6061-T6 billet capability — one-piece and two-piece dome designs machined in-house, with the thermal advantage 6061 holds over 7075 and cast on a small high-revving two-stroke.

• Largest cylinder head manufacturer in Yueqing City — 17,000+ m² facility, 5,000+ tons annual aluminum casting capacity, 125+ CNC machining centers, 26 LPDC machines.

• ISO 9001 certified facility — recognized as a National High-Tech Enterprise and a Technology-Based SME of Zhejiang Province, supplying listed motorcycle brands under multi-year OEM contracts.

Get a Quote for Your YZ85 Cylinder Head Requirements

Send your YZ85 model year (and whether standard or big-wheel YZ85LW, though both use the same head), construction preference (billet, two-piece dome, or cast), and target volume. For performance heads, include your target compression ratio, fuel grade, squish clearance, piston model, and base-gasket thickness so we set the stack correctly. For OEM and private-label programs, include drawings (STEP/IGES) and any anodizing or engraving requirements. Our engineering team responds within 24 hours.