YAMAHA 3L51512100 Yamahopper Right Crank Crankcase Bottom QT50 End

( Manufacturer Part Number: 3L51512100 ), ( Part Type: Crank Case ), ( Compatible Make: For Yamaha ), ( Oe/oem Part Number: 3l5-15121-00 ), ( Compatible Model: Yamahopper ), ( Vintage Part: Yes ), ( Universal Fitment: No ), ( Country Of Origin: Japan ), ( Placement On Vehicle: Right )

Review YAMAHA Yamahopper Right Crank Case Crankcase Bottom End Oem fits 1985

The **Yamaha 3L51512100 1985 Yamaha Hopper QT50 Right Crank Crankcase Bottom End** is a meticulously crafted, high-performance component designed exclusively for the iconic Yamaha QT50, a legendary 50cc trail bike that blends rugged off-road capability with the timeless charm of classic Japanese engineering. This specific part, the **right crank crankcase bottom end**, represents the heart of the engine s lower assembly, where precision and durability converge to deliver reliable power and smooth operation. Crafted from high-grade cast iron, this component is engineered to withstand the demands of off-road riding, including rough terrain, heavy loads, and prolonged use, ensuring longevity and consistent performance. The crankcase bottom end houses the crankshaft, connecting rod bearings, and oil passages, all of which are critical for maintaining optimal engine function. Its design incorporates tight tolerances and precise machining to minimize friction, reduce wear, and maximize efficiency, allowing the QT50 s air-cooled single-cylinder engine to rev smoothly and deliver the responsive power characteristic of Yamaha s mid-1980s motorcycles. Whether restoring a vintage Hopper or upgrading an existing bike, this part is essential for preserving the authenticity and performance of the original build, offering a seamless fit and the same level of reliability that Yamaha was renowned for during its heyday. For enthusiasts seeking to preserve or enhance the mechanical integrity of their 1985 Yamaha QT50, this crankcase bottom end is a must-have, embodying the perfect blend of heritage and engineering excellence.

### **Pros and Cons of Buying a 1985 Yamaha YH-QT50 (3L51512100) Bottom End (Crankcase Crank Right Crankshaft)**

1. **Reliability and Proven Design** The Yamaha YH-QT50 was a well-regarded 50cc motorcycle in its time, known for its simplicity and durability. The bottom end components (crankcase, crankshaft, and bearings) were designed to last with proper maintenance.

2. **Ease of Repair and Maintenance** Being an older, simpler engine, parts are widely available, and mechanics familiar with small two-stroke engines can easily work on it. The bottom end is straightforward compared to modern high-performance engines.

3. **Cost-Effective Replacement** If the rest of the bike is in good condition, replacing just the bottom end is cheaper than buying a complete engine or a new bike. A used or rebuilt bottom end can be significantly cheaper than OEM parts.

4. **Customization Potential** If you plan to modify the bike (e.g., upgrading the carburetor, exhaust, or clutch), a solid bottom end is a good foundation. Some aftermarket parts are available for the QT50.

5. **Nostalgia and Collectibility** If you appreciate classic motorcycles, restoring or modifying a 1985 Yamaha could be a rewarding project. Some collectors value older Yamaha models, especially well-preserved ones.

6. **Lightweight and Simple** The QT50 was designed for ease of use, making it a good choice for beginners or casual riders. A rebuilt bottom end keeps this advantage.

7. **Potential for Performance Gains** With the right modifications (e.g., porting the cylinder, upgrading the carb, or using a high-performance crank), you could improve power output while keeping the stock bottom end intact.

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1. **Age and Wear** A 38-year-old engine is likely to have significant wear, especially in the bearings, crankshaft journals, and cylinder bore. If not properly maintained, the bottom end may require extensive rebuilding.

2. **Availability of Parts** While basic components are still available, finding exact replacements (especially for rare or discontinued parts) can be difficult. Some seals, gaskets, and bearings may need to be sourced from specialty suppliers.

3. **Potential for Hidden Damage** Without a thorough inspection, you might not notice issues like bent crankshafts, worn main bearings, or cracked crankcases. A professional rebuild is recommended to ensure reliability.

4. **Fuel and Emissions Concerns** Modern fuel contains additives that can degrade older rubber seals and gaskets. Running the bike on modern fuel may require additional maintenance or modifications.

5. **Limited Power Potential** The stock bottom end is not designed for high-performance use. Pushing it too hard (e.g., with aggressive mods) could lead to premature failure.

6. **Resale Value** Even a restored QT50 may not hold significant resale value, as modern bikes are more desirable for most buyers.

7. **Maintenance Requirements** Two-stroke engines like the QT50 require regular oil mixing, chain maintenance, and tune-ups. If you re not willing to put in the effort, the bike may become unreliable over time.

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### **Conclusion and Recommendation**

- **Plan to rebuild it professionally** (to ensure longevity and reliability).

- **Have access to the right tools and parts** (or are willing to source them).

- **Are restoring the bike for personal use or nostalgia** rather than resale.

- **Understand the limitations** of the engine and are prepared for maintenance.

However, if you re looking for a **low-maintenance, high-performance, or modern bike**, this bottom end may not be the best choice. The QT50 is a **project bike** ideal for enthusiasts who enjoy mechanical work and classic motorcycles.

- **If you re experienced with engine rebuilds and want a classic bike**, purchasing the bottom end (or a complete rebuilt engine) is a good investment.

- **If you re a beginner or prefer convenience**, consider buying a **complete restored QT50** or a **modern 50cc bike** instead.

- **Always inspect the crankcase for cracks, measure crankshaft runout, and check bearings** before purchasing to avoid costly surprises.

Would you like guidance on where to source parts or how to inspect the bottom end?

Details:

May fit other years and model's please verify compatibility before purchasing. Removed from a 1985 Yamaha QT50. Good used condition with typical signs of wear. OEM Part from 1985 Yamaha QT50.

See images for a more accurate assessment of the parts condition.

part #: 3l51512100 prices

• $29.94-$166.58

specifications cyclevintagee:

• for makes: Yamaha
• for years: 1985
• mpn: 3l51512100
• part type: Crank Case
• compatible make: For Yamaha
• oe/oem part number: 3l5-15121-00
• compatible model: Yamahopper
• vintage part: Yes
• universal fitment: No
• country of origin: Japan
• placement on vehicle: Right

shipping cyclevintagee:

• transit: 4-9 Days
• carrier: USPS
• cost: $0.00
• type: Fixed
• class: Standard
• service: USPS Ground Advantage

returns cyclevintagee:

• policy: No Returns

offer cyclevintagee:

• availability: In Stock
• sold: 0
• quantity: 1
• started: April 18, 2026
• options: Ship-to-home

seller cyclevintagee:

• rating: 99.9%
• city: Rochester, Michigan
• # reviews: 2406

payments cyclevintagee:

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

general cyclevintagee:

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

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