HARLEY-DAVIDSON 3972-35 Thrust Bearing Cover Hub 1935-UP 45 P598

( Brand: Harley-davidson ), ( Manufacturer Part Number: 3972-35 ), ( Part Type: Bearing Cover Hub ), ( Compatible Make: For Harley-davidson ), ( Oe/oem Part Number: 3972-35, 43566-35a ), ( Compatible Model: Servi-car ), ( Country Of Origin: United States ), ( Placement On Vehicle: Rear )

Review HARLEY DAVIDSON Oe 1935-up Thrust Bearing Cover Hub45 Wl fits STAR KNUCKLEHEAD

The **Harley-Davidson 3972-35 1935-Up Thrust Star Bearing Cover Hub for the iconic Knucklehead (P598) engine** is a meticulously crafted, high-performance aftermarket component designed to restore and enhance the legendary functionality of one of the most sought-after Harley-Davidson powerplants ever produced. This precision-machined part is engineered to fit seamlessly onto the **1935 and later Knucklehead engines**, ensuring optimal alignment and performance for the legendary **P598** model, which was the first production Harley-Davidson to feature a monoblock crankcase and overhead valves. The thrust star bearing cover hub is a critical component that supports the crankshaft s thrust bearings, reducing friction, preventing premature wear, and maintaining the engine s smooth, resonant power delivery the hallmark of the Knucklehead s legendary throaty exhaust note and raw torque. Crafted from durable, high-grade materials, this bearing cover hub is designed to withstand the intense heat and stress of high-performance operation, making it an essential upgrade for restorers, collectors, and enthusiasts who demand nothing less than perfection in their classic Harley-Davidson. Whether used in a meticulously restored show bike or a high-revving street machine, this part ensures that the Knucklehead s legendary character remains intact, allowing riders to experience the unmistakable growl and power of one of Harley-Davidson s most influential engines. With its exacting fit and superior craftsmanship, this bearing cover hub is a testament to the enduring legacy of the Knucklehead, bridging the gap between vintage authenticity and modern reliability.

### **Pros and Cons of buying a Harley-Davidson 1935 Knucklehead (Model 3972-35) Thrust Star Bearing Cover, Hub, and 45 Knucklehead Parts (P598)**

#### **Pros**

1. **Authentic Vintage Restoration** This part is designed for the original 1935 Harley-Davidson Knucklehead engine, making it ideal for collectors and enthusiasts seeking genuine period-correct components. The Knucklehead is one of the most iconic Harley engines ever made, and restoring it with original or high-quality reproduction parts enhances its value and authenticity.

2. **High-Quality Materials (If Reproduction)** While the original parts may be rare, modern reproduction parts (if available from reputable manufacturers like **Harley-Davidson Restoration Parts, Knucklehead Specialties, or Evo**) are often made to exact specifications, ensuring proper fit and function. Some aftermarket suppliers use high-grade steel and precision machining to match the original build quality.

3. **Increased Engine Longevity** The **thrust star bearing cover, hub, and 45 Knucklehead parts** are critical components that support the crankshaft and camshaft. Properly fitted and maintained parts reduce wear, prevent premature failure, and help preserve the engine s performance over time.

4. **Enhanced Aesthetic Appeal** The Knucklehead engine is a legendary design, and restoring it with correct parts improves its visual appeal. This is particularly valuable for show bikes, museum pieces, or high-end restorations where authenticity matters.

5. **Potential for Increased Resale Value** A fully restored Knucklehead with original or high-quality reproduction parts can significantly increase the bike s value, especially in the vintage Harley market. Well-maintained Knuckleheads are highly sought after by collectors.

6. **Historical Significance** Owning and restoring a Knucklehead allows enthusiasts to preserve a piece of motorcycle history. The engine s design influenced later Harley models, and maintaining it keeps that legacy alive.

7. **Customization Flexibility** While the parts are period-correct, some enthusiasts modify them (within reason) for improved performance or durability. For example, upgrading bearings or seals can enhance reliability without compromising the engine s classic look.

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#### **Cons**

1. **High Cost (Original Parts)** Original 1935 Harley-Davidson parts are extremely rare and often command high prices due to their age and scarcity. If you find them, expect to pay **hundreds or even thousands of dollars** depending on condition and rarity.

2. **Limited Availability (Reproduction Parts)** While some reproduction parts exist, not all components may be easily accessible. The **thrust star bearing cover, hub, and 45 Knucklehead-specific parts** may require special ordering, and lead times can be long. Some suppliers may no longer produce certain Knucklehead-specific items, forcing buyers to seek alternatives.

3. **Difficulty in Installation** The Knucklehead engine is complex, and installing these parts may require **advanced mechanical skills, specialized tools, or professional help**. Misalignment or improper fitting can lead to engine damage, so inexperienced builders should proceed with caution.

4. **Maintenance Challenges** Vintage Harley engines, even with modern parts, require **more frequent maintenance** than modern bikes. The Knucklehead s design is less forgiving of neglect, and components like bearings, seals, and valves may wear out faster if not properly cared for.

5. **Reliability Concerns (Original Parts)** Original parts from the 1930s may have **wear, corrosion, or manufacturing inconsistencies**. If sourced from a non-authentic or poorly preserved source, they could fail prematurely, leading to costly repairs.

6. **Limited Performance Compared to Modern Standards** While the Knucklehead is a legendary engine, it is **not as powerful or refined** as modern Harley engines. Expect **lower torque, less fuel efficiency, and more vibration** compared to contemporary bikes. This may not be ideal for daily riding unless the bike is strictly for show or weekend cruising.

7. **Insurance and Legal Considerations** Vintage motorcycles, especially restored ones, may have **higher insurance costs** due to their value. Additionally, some modern laws or insurance policies may not cover classic bikes as easily as modern vehicles.

8. **Time-Consuming Restoration** Restoring a Knucklehead to running condition can take **months or even years**, depending on the bike s condition. This requires patience, dedication, and often a significant investment in labor and parts.

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### **Conclusion**

Buying **Harley-Davidson 1935 Knucklehead parts (thrust star bearing cover, hub, and 45 Knucklehead components)** is a **highly rewarding but challenging** endeavor. The decision ultimately depends on your **goals, budget, and level of commitment**.

If you are a **collector, restorer, or enthusiast** who values **authenticity, history, and the challenge of working with a legendary engine**, these parts are worth pursuing. The **emotional and historical satisfaction** of owning a restored Knucklehead far outweighs the challenges for many.

However, if you are looking for a **practical, high-performance, or low-maintenance** motorcycle, a Knucklehead may not be the best choice. The **cost, complexity, and time investment** make it more suitable for **weekend projects, show bikes, or investment pieces** rather than daily transportation.

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### **Recommendation**

- **Source parts from reputable suppliers** (Harley-Davidson Restoration Parts, Knucklehead Specialties, or trusted aftermarket manufacturers).

- **Budget for professional help** if mechanical skills are limited.

- **Allocate sufficient time** restoration is a marathon, not a sprint.

- **Consider a less rare Knucklehead model** (e.g., 1936-1941) if the 1935 parts are too expensive or hard to find.

- Start with a **lesser-known vintage Harley** (e.g., a 1950s Panhead or 1960s Shovelhead) to gain experience before tackling a Knucklehead.

- Consider **modern Harley-Davidson models** if you want a reliable, high-performance bike without the restoration challenges.

- Focus on **fully restored Knuckleheads** with **original or high-quality reproduction parts** to maximize resale value.

- Join **vintage Harley forums (e.g., Knucklehead Specialties, Harley-Davidson Restoration Groups)** for advice and part sourcing.

**Final Verdict:** The **1935 Knucklehead parts are a fantastic investment for the right buyer** one who appreciates craftsmanship, history, and the thrill of working with a piece of motorcycle legend. However, they are **not for the faint of heart or budget**. If you are prepared for the challenges, the reward of owning a **fully restored Knucklehead** is unmatched in the motorcycle world.

Details:

For Sale is: OEM 1935-up Star Hub Thrust Bearing, Covers # 3972-35, or 43566-35A. This is in Good Condition, New Pauperizing. These are the Later version with Grease nipple.

part #: 397235 prices

• $42.70-$49.00

specifications cyclevintagee:

• for models: Star, Knucklehead
• for makes: Harley
• brand: Harley-davidson
• mpn: 3972-35
• part type: Bearing Cover Hub
• compatible make: For Harley-davidson
• oe/oem part number: 3972-35, 43566-35a
• compatible model: Servi-car
• country of origin: United States
• placement on vehicle: Rear

offer cyclevintagee:

• sold: 0
• availability: In Stock
• started: March 21, 2026
• options: Ship-to-home
• quantity: 1

general cyclevintagee:

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

seller cyclevintagee:

• city: Watsonville, California
• rating: 99.7%
• # reviews: 2300

returns cyclevintagee:

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

payments cyclevintagee:

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

shipping cyclevintagee:

• service: USPS Ground Advantage
• transit: 5-12 Days
• class: Standard
• type: Calculated
• carrier: USPS
• cost: $0.00

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