KAWASAKI 59051-1205 Exhaust Valve Idle Gear

( Manufacturer Part Number: 59051-1205 ), ( Part Type: Valve Exhaust Gear ), ( Country Of Origin: Japan )

Review KAWASAKI Exhaust Valve Idle Gear fits SPUR KX500 1989–2004

The **Kawasaki 59051-1205 Exhaust Valve Spur and Idle Gear Assembly** for the **1989 2004 KX500** is a critical, high-performance component designed to ensure optimal engine function, reliability, and longevity in one of motocross s most legendary dirt bikes. This meticulously engineered part is a direct-fit replacement for the stock valve spur and idle gear mechanism, which drives the exhaust valve lifter and regulates idle speed in the KX500 s renowned **DOHC (Dual Overhead Camshaft)** engine. Crafted from precision-machined steel, the **exhaust valve spur** features a hardened, durable gear tooth profile that minimizes wear and backlash, allowing for smoother valve operation and reduced friction essential for maintaining peak performance under the extreme stresses of high-revving, high-torque motocross riding. The accompanying **idle gear** is equally critical, as it governs the bike s idle speed and throttle response, ensuring a consistent and stable engine idle that s both reliable and adjustable for fine-tuning. Together, these components are integral to the KX500 s legendary **100 horsepower** output and its reputation for being one of the most durable and tunable engines in its class. Whether used for restorative maintenance, performance upgrades, or as a preventive replacement to avoid premature wear, this assembly is a must-have for riders seeking to preserve the integrity of their KX500 s drivetrain. Its compatibility with the bike s **1989 2004 model years** including variations like the **KX500F, KX500R, and KX500X** makes it a versatile solution for both stock and modified setups, ensuring that the engine s critical valve train remains in peak condition for years of aggressive riding.

### Pros and Cons of buying a Kawasaki 59051-1205 (1989 2004 KX500 Exhaust Valve, Spur Idle Gear)

1. **Common and Widely Available** The KX500 was a popular dirt bike in its era, so replacement parts like the exhaust valve and idle gear are relatively easy to source. Dealers, online marketplaces, and aftermarket suppliers frequently stock these components.

2. **Budget-Friendly** Compared to OEM parts, aftermarket alternatives (such as those from **Kawasaki, Yoshi s, or other reputable brands**) are often affordable, making this a cost-effective upgrade or replacement.

3. **Performance Impact** Upgrading the exhaust valve can improve airflow, potentially enhancing throttle response and power output, especially if the original valve was worn or restricted. A new idle gear ensures smoother idle and reduces vibration.

4. **Preventative Maintenance** Replacing these parts as part of routine maintenance can prevent catastrophic engine failure (e.g., a seized valve or broken idle gear) and extend the bike s lifespan.

5. **Compatibility** The 59051-1205 part number is specific to the KX500 s engine, ensuring a direct fit without modification. No custom machining or adapters are typically required.

6. **Durability** High-quality aftermarket or OEM parts are designed to withstand the stresses of off-road use, reducing the likelihood of premature failure.

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1. **Age-Related Wear** If the bike has high mileage or was not well-maintained, the engine may already have internal damage (e.g., piston rings, cylinder wear) that isn t addressed by just replacing the valve and idle gear. A full inspection is recommended.

2. **Mixed Quality in Aftermarket Parts** While many aftermarket options exist, some may be poorly made, leading to premature failure or improper sealing. Brands like **Yoshi s, K&S, or OEM replacements** are safer bets but may cost more.

3. **Installation Complexity** Replacing the exhaust valve requires removing the cylinder head, which is a labor-intensive process. If the rider lacks mechanical experience, professional labor costs may apply.

4. **Potential for Counterfeit Parts** Cheap knockoff parts (especially from unverified sellers) may not meet Kawasaki s specifications, risking performance issues or damage. Always verify the source.

5. **Limited Longevity Without Full Service** If the bike s oil, filters, and other components are neglected, replacing just these parts won t fully restore reliability. A comprehensive service (e.g., valve adjustment, ring gap check) is ideal.

6. **Market Variability** Prices for these parts can fluctuate based on demand, seller location, and condition. Buying from a trusted supplier (e.g., **RockAuto, DirtBikeParts, or a local Kawasaki dealer**) helps avoid scams or overpricing.

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The Kawasaki 59051-1205 exhaust valve and idle gear are practical and necessary components for maintaining or upgrading a 1989 2004 KX500. Their advantages lie in accessibility, cost-effectiveness, and performance benefits, but their effectiveness depends on the bike s overall condition and the quality of the parts installed. If the bike is otherwise healthy, these replacements are a smart investment. However, if the engine shows signs of broader wear (e.g., blue smoke, rough idle, loss of power), a full diagnostic or rebuild may be warranted.

- **Buy from a reputable source** (e.g., OEM Kawasaki parts, Yoshi s, or well-reviewed aftermarket brands) to ensure quality.

- **Pair this purchase with a professional inspection** to check for other potential issues (e.g., piston rings, crankshaft wear).

- **Consider a full valve job** (including seat machining and lapping) if the bike has high mileage, as this can restore performance better than just replacing individual parts.

- **Document the installation** and follow Kawasaki s maintenance schedule to maximize longevity.

- **If DIYing, invest in quality tools** (e.g., torque wrench, valve spring compressor) to avoid mistakes during installation.

For most riders, replacing these components is a worthwhile upgrade, but prioritize the bike s overall health to avoid recurring issues.

Details:

This is a Spur idle gear from 1990 Kawasaki KX500. I always do my best to combine shipping on multiple items. Kawasaki part number is 59051-1205. It MAY fit the following model's: 1989 2004 KX500.

The domestic shipping price listed is for the lower 48 states only.

part #: 590511205 prices

• $83.95-$250.00

specifications valvemotorcycleaz:

• for models: Kx500, Spur
• for makes: Kawasaki
• for years: 1989-2004
• mpn: 59051-1205
• part type: Valve Exhaust Gear
• country of origin: Japan

shipping valvemotorcycleaz:

• type: Fixed
• carrier: USPS
• cost: $0.00
• service: USPS Ground Advantage, USPS Priority Mail
• transit: 3-8 Days
• class: Standard, Expedited

general valvemotorcycleaz:

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

seller valvemotorcycleaz:

• # reviews: 14244
• rating: 99.9%
• city: Onsted, Michigan

offer valvemotorcycleaz:

• options: Ship-to-home
• availability: In Stock
• started: April 13, 2026
• quantity: 1
• sold: 0

payments valvemotorcycleaz:

• wallet: Paypal
• credit card: Mastercard
• other

returns valvemotorcycleaz:

• policy: Returns Accepted
• paid by: Buyer
• time: 14 Days

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