DUCATI 21010035A Intake Inlet Valve Head Stem 43MM 8MM 900SS

( Manufacturer Part Number: 21010035A ), ( Part Type: Intake Valve Head ), ( Country Of Origin: Italy )

Review DUCATI Intake Inlet Valve 43mm Head 8mm Stem 900ss fits MONSTER ST2 900

The **Ducati 21010035A Intake Inlet Valve** is a precision-engineered component designed exclusively for high-performance Ducati motorcycles, specifically tailored to the **Monster 900 ST2** and **Monster 900S**, ensuring optimal airflow and combustion efficiency within the engine s cylinder head. Crafted from high-grade **forged aluminum alloy**, this **43mm head diameter** valve features a **diameter-stem combination of 8mm**, a dimension meticulously calibrated to maintain the factory s intended valve train dynamics while delivering enhanced breathing capacity for improved throttle response and power delivery. The valve s **aerodynamic contour** and **precision-machined seat** ensure a tight, consistent seal, minimizing blow-by and maximizing compression, which is critical for sustaining the aggressive, sport-tuned character of the Monster 900 lineup. Whether used for routine maintenance, performance upgrades, or as a direct replacement for a worn or damaged valve, this part adheres to Ducati s stringent engineering standards, guaranteeing compatibility with the **ST2 s** or **S s** **1,098cc L-twin engine** without compromising reliability. Built to withstand the extreme thermal and mechanical stresses of high-revving, high-performance riding, the **21010035A** is a critical component for preserving the engine s longevity while unlocking subtle gains in performance ideal for both enthusiasts seeking a factory-accurate rebuild and tuners looking to fine-tune their Monster s power output.

### **Pros and Cons of buying a Ducati 21010035A Intake Inlet Valve (43mm Head, 8mm Stem) for a Monster 900 ST2/900SS**

1. **Performance Improvement** The 43mm intake valve is designed to enhance airflow into the engine, which can improve throttle response, especially at higher RPMs. This is particularly noticeable in the Monster 900 s naturally aspirated setup, where airflow restrictions can limit power.

2. **Potential Power Gain** Depending on the condition of the stock valve and the rest of the intake system, replacing it with a larger or more efficient valve could yield measurable gains in horsepower and torque, particularly in the mid-to-high RPM range.

3. **Compatibility** The Monster 900 ST2 and 900SS share many engine components, so this valve should fit both models without modification. Ducati s valve design is consistent across these bikes, making aftermarket parts like this a straightforward upgrade.

4. **Durability** Ducati s forged valves are generally robust, and this part appears to be a high-quality aftermarket replacement designed to match or exceed OEM standards. Proper installation and maintenance should ensure longevity.

5. **Cost-Effective Upgrade** Compared to full engine rebuilds or major intake modifications, replacing a single valve is a relatively inexpensive way to experiment with performance tuning. The cost is often justified by the potential gains.

6. **Easy Installation** As a standalone component, this valve can be installed without extensive disassembly of the engine. It may require removing the cylinder head, but this is a manageable task for someone with basic mechanical skills or a trusted mechanic.

7. **Potential for Further Tuning** If the valve upgrade yields positive results, it could serve as a foundation for additional modifications, such as porting the cylinder head or upgrading the intake manifold, to further enhance performance.

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1. **Limited Power Gains Without Supporting Modifications** While the valve itself may improve airflow, the Monster 900 s engine is already well-tuned by Ducati. Without complementary upgrades (e.g., a high-flow air filter, tuned ECU, or exhaust system), the gains from this valve alone may be modest. Expect noticeable improvements only if the rest of the intake system is optimized.

2. **Risk of Engine Stress** Increasing airflow without adjusting fuel delivery (via a remap or fuel system upgrade) can lead to lean conditions, particularly at high RPMs. This could cause detonation, reduced reliability, or even engine damage if the bike is pushed too hard without proper tuning.

3. **Potential for Voiding Warranty** If the bike is still under warranty, installing aftermarket parts like this valve may void coverage. Ducati s warranty policies typically require OEM parts, so this is a risk to consider if the bike is new or under warranty.

4. **Skill Dependency** Installing a valve requires removing the cylinder head, which involves precision work. Improper installation such as incorrect seating, gasket damage, or torque specifications could lead to leaks, poor sealing, or even head gasket failure. Those without mechanical experience may need to pay a mechanic, adding to the cost.

5. **Mixed Results Based on Stock Condition** If the stock valve is already worn or damaged, the upgrade may not yield significant benefits. Conversely, if the stock valve is near-perfect, the gains could be minimal. This makes it a "maybe worth it" upgrade rather than a guaranteed performance boost.

6. **Compatibility with Other Mods** If the bike has other intake or exhaust modifications (e.g., a cold air intake or aftermarket exhaust), the valve upgrade may interact unpredictably with those components. Testing and tuning may be required to achieve optimal results.

7. **No Guarantee of Noticeable Difference** The Monster 900 ST2/900SS is already a capable bike, and the power gains from a single valve upgrade may be subtle unless paired with other mods. Riders looking for dramatic performance jumps may find this upgrade underwhelming.

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The Ducati 21010035A intake inlet valve (43mm head, 8mm stem) is a **low-risk, moderate-reward upgrade** for the Monster 900 ST2 or 900SS. It offers a straightforward way to experiment with airflow improvements without major engine work, but its effectiveness depends heavily on complementary modifications and proper tuning.

If you re already planning to upgrade other intake or exhaust components, this valve could be a worthwhile addition to the package. However, if you re looking for a standalone "quick win," the gains may be modest unless you re willing to invest in additional tuning or mods.

For **enthusiasts who enjoy tinkering and have a plan for further tuning**, this valve is a solid choice. For **casual riders or those seeking dramatic power gains**, it may not be the most impactful upgrade on its own.

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- You re already modifying other intake or exhaust components (e.g., adding a high-flow air filter, tuning the ECU, or upgrading the exhaust).

- You have access to a mechanic or are comfortable with cylinder head removal and valve installation.

- You re open to testing and tuning the bike afterward to ensure optimal performance and fuel delivery.

- You re looking for a "plug-and-play" performance boost without additional work.

- The bike is still under warranty, as aftermarket parts may void coverage.

- You lack experience with engine modifications and aren t willing to pay for professional installation and tuning.

If you re unsure about the valve alone, consider a **full intake manifold upgrade** or a **cylinder head porting kit**, which can provide more substantial airflow improvements. However, these are more involved and expensive.

Ultimately, this valve is best suited for **intermediate riders who want to explore performance tuning incrementally**. For maximum results, pair it with a **remap or fuel system upgrade** to avoid lean conditions.

Details:

This item is in good condition and comes as shown the photos. 43mm Intake Valve to fit all Ducati 900 2v model's '91 Later as well the ST2 Ducati p/n 21010035A.

part #: 21010035a prices

• $80.00-$178.94

specifications valvemotorcycleaz:

• for models: St2, 900, Monster
• for makes: Ducati
• mpn: 21010035a
• part type: Intake Valve Head
• country of origin: Italy

seller valvemotorcycleaz:

• city: Clermont, Florida
• rating: 99.9%
• # reviews: 24081

general valvemotorcycleaz:

• condition: Used
• Engines Engine Parts > Valvetrain Components > Engine Valves

returns valvemotorcycleaz:

• policy: No Returns

offer valvemotorcycleaz:

• options: Ship-to-home
• availability: In Stock
• best offers: True
• started: February 22, 2026
• quantity: 1
• sold: 0

payments valvemotorcycleaz:

• credit card: Mastercard
• other
• wallet: Apple-pay

shipping valvemotorcycleaz:

• carrier: UPS
• service: Standard, UPS 2nd Day Air
• transit: 3-6 Days
• type: Fixed
• cost: $0.00
• class: Standard, Expedited

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