YAMAHA 1M2-17421-00-00 Transmission Counter Shaft Drive Axle Gears

( Manufacturer Part Number: 1M2-17421-00-00 ), ( Vintage Part: Yes )

Review YAMAHA Transmission Counter Shaft Drive Axle And Gears fits YZ250 YZ400 IT400 1977–1978

The **Yamaha 1M2-17421-00-00 Transmission Countershaft Drive Axle Gears** is a meticulously engineered set of critical components designed exclusively for the **1977 and 1978 Yamaha YZ250, YZ400, and IT400** models, ensuring optimal performance, durability, and reliability for these iconic two-stroke dirt bikes. This high-quality gear assembly serves as the backbone of the transmission system, facilitating smooth power transfer from the engine to the rear wheel while withstanding the intense stresses of off-road riding. Crafted from precision-machined steel, these gears are heat-treated and dynamically balanced to minimize vibration and wear, even under the most demanding conditions. The countershaft assembly incorporates a series of finely cut, hardened teeth that mesh seamlessly with the primary and final drive gears, delivering efficient torque transfer with minimal friction. The drive axle gears, in particular, are designed to handle the aggressive forces generated by the high-revving, two-stroke engines of these bikes, ensuring consistent engagement and preventing premature failure. Whether restoring a classic YZ to its original glory or upgrading an existing setup for enhanced durability, this OEM replacement part guarantees a perfect fit and the same level of performance as the original equipment. Ideal for mechanics, enthusiasts, and customizers, these gears are a must-have for anyone seeking to maintain or improve the drivetrain integrity of their Yamaha YZ or IT400 from the late 1970s.

### **Pros and Cons of Buying a 1977-1978 Yamaha YZ250/YZ400/IT400 Transmission Countershaft Drive Axle Gears (Part #1M2-17421-00-00)**

1. **Compatibility with Classic Yamaha Engines** This transmission and countershaft assembly is designed specifically for the 1977-1978 Yamaha YZ250, YZ400, and IT400 models, ensuring a proper fit without modification.

2. **Reliability for Vintage Racing** Yamaha s early 1970s transmissions were built to withstand high-stress racing conditions, making them a solid choice for restoration or competition use.

3. **Availability of Replacement Parts** Since these bikes were popular in their time, finding OEM or aftermarket parts (such as seals, bearings, and gears) is relatively easier than for more obscure models.

4. **Historical Accuracy for Restoration** If you re restoring a bike to factory specifications, using the original transmission ensures authenticity.

5. **Potential for Modification** The countershaft and gear setup can sometimes be upgraded with aftermarket parts (e.g., stronger gears, custom chains) for improved performance.

6. **Lower Cost Compared to Modern Components** Since these parts are older, they are generally cheaper than contemporary transmissions, making them a budget-friendly option for enthusiasts.

1. **Age-Related Wear** Even if the part is in good condition, the age of the components (especially bearings, seals, and synchronizers) may mean they require frequent maintenance or replacement.

2. **Limited Availability of New Stock** Yamaha no longer produces these exact parts, so sourcing them may require searching used markets, eBay, or specialty vintage bike shops.

3. **Potential for Misalignment Issues** If the bike s frame or engine mounts have been modified or weakened over time, the transmission may not fit perfectly, leading to shifting problems or excessive play.

4. **Lack of Modern Upgrades** Unlike newer transmissions, these older units do not benefit from modern advancements in gear materials, clutch technology, or shift mechanisms, which could affect durability.

5. **Compatibility with Modified Engines** If the engine has been heavily modified (e.g., increased displacement, forced induction), the stock transmission may struggle with power delivery, leading to premature wear.

6. **Difficulty in Finding a Fully Functional Unit** Many used transmissions in this condition may have internal damage (bent shafts, worn gears, or seized bearings), requiring disassembly and inspection before installation.

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### **Conclusion**

The **Yamaha 1M2-17421-00-00 transmission and countershaft assembly** is a solid choice for **restoration projects, vintage racing, or enthusiasts who prioritize authenticity** over modern performance. It offers **historical accuracy, reliability for its era, and relative affordability**, but buyers should be prepared for **potential wear, limited new stock availability, and the need for careful inspection** before installation.

If your primary goal is **competition or daily riding with modern performance expectations**, you may need to supplement this transmission with **aftermarket upgrades** (e.g., stronger gears, modern clutches, or reinforced shafts). However, for **purists or those restoring a classic bike**, this part remains a **valuable and functional component** of Yamaha s early 1970s motocross and trail bikes.

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### **Recommendation**

- **Buy if:** You are restoring a **1977-1978 Yamaha YZ250/YZ400/IT400** to stock specifications, need a **budget-friendly transmission**, or are participating in **vintage racing** where authenticity matters.

- **Inspect thoroughly before purchase:** Check for **bent shafts, worn gears, seized bearings, and proper alignment** consider disassembling it if possible.

- **Consider alternatives if:** You plan to **modify the engine significantly** (e.g., big bore kits, forced induction) or want **modern durability and performance**.

- **Pair with complementary parts:** If restoring, source **OEM or high-quality aftermarket seals, synchronizers, and bearings** to extend the transmission s lifespan.

For most **enthusiasts working on original bikes**, this part is a **wise investment** just be prepared for **maintenance and potential upgrades** to keep it running smoothly.

Details:

Manufactured by Yamaha, this part is a genuine replacement piece that ensures smooth and efficient gear shifting in the motorcycle. The Yamaha YZ250 YZ400 IT400 Transmission Counter Shaft Drive Axle Gears is a vintage part designed for motorcycles from the years 1977 and 1978. This product includes a transmission counter shaft drive axle and gears specifically compatible with Yamaha model's. Perfect for maintenance and restoration projects, this high-quality transmission component is a reliable choice Yamaha motorcycle owners looking to keep their vehicle in top condition.

part #: 1m2174210000 prices

• $49.95-$129.00

specifications cyclevintagee:

• for models: Yz250, Yz400, It400
• for makes: Yamaha
• for years: 1977-1978
• mpn: 1m2-17421-00-00
• vintage part: Yes

returns cyclevintagee:

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

offer cyclevintagee:

• options: Ship-to-home
• availability: In Stock
• quantity: 1
• best offers: True
• sold: 0
• started: March 30, 2026

seller cyclevintagee:

• # reviews: 62
• city: Burley, Idaho
• rating: 100.0%

general cyclevintagee:

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

payments cyclevintagee:

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

shipping cyclevintagee:

• service: USPS Ground Advantage
• cost: $8.38
• transit: 4-11 Days
• type: Calculated
• carrier: USPS
• class: Standard

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