HONDA 90031-KCY-670 Cylinder Head Stud Bolt Set

( Manufacturer Part Number: 90031-KCY-670 ), ( Type: Stud Bolt ), ( Country Of Origin: Japan )

Review HONDA Oem Cylinder Head Stud Bolt Set fits SPORTRAX 400 1999–2008

The **Honda 90031-KCY-670 Cylinder Head Stud Bolt Set** is a precision-engineered, high-performance replacement part designed exclusively for the **1999 2008 Honda SportRax 400** (and its variants, including the 400i and 400S models) equipped with the **F23A1 or F23A2 2.3L inline-four engine**. This meticulously crafted bolt set is a critical component for maintaining optimal engine performance, reliability, and longevity, particularly after high-mileage use, engine modifications, or when addressing issues like cylinder head warping, gasket leaks, or compression loss. Engineered to Honda s exacting specifications, these **Grade 12.9 high-strength studs** feature a **fine-threaded, 6mm x 1.0mm pitch** design, ensuring a secure and uniform clamping force across the cylinder head and block interface. Each stud is forged from **chromoly steel**, a material renowned for its superior tensile strength, fatigue resistance, and ability to withstand extreme temperatures qualities essential for the demanding thermal and mechanical stresses encountered in high-revving, turbocharged, or naturally aspirated applications. The set includes **eight (8) studs**, complete with **new washers** (where applicable), and is often recommended by mechanics and tuners as a proactive measure to prevent catastrophic engine failure, especially in scenarios where original equipment bolts have stretched or corroded over time. Whether you're performing a **full cylinder head rebuild**, addressing a **blown head gasket**, or simply upgrading your engine s critical fasteners for added durability, this bolt set delivers the precision and robustness required to restore factory-level integrity or exceed it while ensuring a proper seal between the head and block. Built to withstand the rigors of modern performance driving, these studs are a small but vital investment in preserving the reliability and efficiency of your SportRax s powerplant.

### **Pros and Cons of buying a Honda 90031-KCY-670 (1999-2008 SportRax 400 Cylinder Head Stud Bolt Set)**

1. **OEM Quality and Fit** This is a genuine Honda part, meaning it is designed to match the exact specifications of the original equipment. It ensures proper sealing, torque application, and long-term reliability when installed correctly.

2. **Durability and Performance** Honda s cylinder head studs are built to withstand high engine temperatures and stress, which is crucial for maintaining compression and preventing leaks over time. High-quality studs reduce the risk of warping or failure under heavy loads.

3. **Compatibility** The part is specifically engineered for the 1999-2008 Honda SportRax 400 engine, ensuring a perfect fit without modifications. This eliminates the guesswork that comes with aftermarket or mismatched parts.

4. **Warranty Coverage** As an OEM part, it may come with Honda s warranty (if purchased directly from an authorized dealer or Honda s official parts distributor), providing peace of mind against defects.

5. **Prevents Future Issues** Worn or damaged studs can lead to cylinder head leaks, compression loss, or even catastrophic engine failure. Replacing them proactively can extend the life of the engine and avoid costly repairs down the line.

6. **Professional-Grade Installation** Since this is a standard replacement part, mechanics and DIYers with proper tools (torque wrench, head gasket kit, and experience) can install it without major complications.

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1. **Cost** OEM parts are typically more expensive than aftermarket alternatives. The price of this stud bolt set may be higher than generic or third-party options, which could be a deterrent for budget-conscious buyers.

2. **Limited Availability** While Honda still supports older models, genuine parts may not be as readily available as they once were. Purchasing from a reputable dealer or online marketplace (e.g., RockAuto, Honda s official site) is essential to avoid counterfeit or low-quality fakes.

- Removing the cylinder head (which involves disconnecting various components like fuel lines, sensors, and cooling hoses).

- Cleaning the head and block surfaces thoroughly to prevent warping.

- Applying the correct torque sequence and specifications (typically 60-70 ft-lbs for initial tightening, followed by 90-100 ft-lbs for final torque).

- Using a new head gasket and proper sealing compounds.

This is not a beginner-friendly job and may require professional help, adding to labor costs.

4. **Potential for Over-Tightening** Improper torque can strip threads or warp the head, leading to leaks or engine damage. Even with a torque wrench, inexperienced installers may struggle to achieve the correct specification.

5. **Time-Consuming** The process of removing the head, installing new studs, and reassembling everything can take several hours, depending on the mechanic s experience. This may not be ideal for those with limited time or patience.

6. **Alternative Options Exist** Aftermarket stud bolt sets (e.g., from ARP, MEGA, or other reputable brands) may offer similar performance at a lower cost. Some aftermarket studs are even stronger than OEM parts, though they must be installed with the correct torque settings.

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The **Honda 90031-KCY-670 cylinder head stud bolt set** is a reliable, high-quality choice for maintaining or restoring the performance of a 1999-2008 SportRax 400 engine. Its OEM status ensures compatibility, durability, and peace of mind, making it ideal for those who prioritize long-term engine health and want to avoid potential issues from inferior parts. However, the higher cost, installation complexity, and time commitment are significant drawbacks, particularly for casual DIYers or those on a tight budget.

If the engine is showing signs of stud wear (e.g., oil leaks, compression loss, or difficulty starting), replacing them is a proactive measure to prevent more severe damage. For those willing to invest in quality and have the skills or access to professional help, this is a strong recommendation. Alternatively, if cost is a major concern, a **high-quality aftermarket stud set** (e.g., ARP or MEGA) could be a viable alternative, provided the correct installation procedures are followed.

- You value genuine Honda quality and want to avoid compatibility issues.

- You are prepared to invest in professional installation or have experience with cylinder head work.

- Your engine is showing clear signs of stud wear (e.g., oil leaks, compression problems).

- You want warranty coverage (if purchasing from an authorized source).

- You are on a tight budget and can find a reputable brand with similar specifications.

- You are confident in your mechanical skills and can follow precise installation guidelines.

- You are replacing studs purely for preventive maintenance and the engine is otherwise healthy.

For most owners, the **OEM part is the safest choice**, but weigh the pros and cons against your budget, time, and mechanical comfort level before deciding. Always source the part from a trusted dealer to avoid counterfeit or damaged inventory.

Details:

M-force race crafts. Removed From: 2004 Honda Sportrax 400 TRX400EX 2x4 with miles, Please review all pictures to assess the condition of item. 99-08 HONDA SPORTRAX 400 OEM CYLINDER HEAD STUD BOLT SET, PROBLEM.

part #: 90031kcy670 price

• $19.95

specifications cyclevintagee:

• for models: 400, Sportrax
• for makes: Honda
• for years: 1999-2008
• mpn: 90031-kcy-670
• type: Stud Bolt
• country of origin: Japan

general cyclevintagee:

• Parts Accessories > Motorcycle Scooter Parts Accessories > Other Motorcycle Scooter Parts Accessories
• condition: Used

offer cyclevintagee:

• best offers: True
• sold: 0
• started: May 9, 2026
• availability: In Stock
• options: Ship-to-home
• quantity: 1

seller cyclevintagee:

• # reviews: 1780
• rating: 99.6%
• city: Las Vegas, Nevada

returns cyclevintagee:

• policy: Returns Accepted
• time: 30 Days
• paid by: Seller

payments cyclevintagee:

• wallet: Google-pay
• credit card: Discover
• other

shipping cyclevintagee:

• cost: $0.00
• transit: 5-10 Days
• class: Standard
• type: Fixed
• service: Standard

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