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  3. HARDDRIVE MN/JT5S

HARDDRIVE MN-JT5S Throttle Slide Vacuum Membrane Hq MN/JT5S

fits model: Flstf. make: Harley, Davidson. year: 1990–2006.

Jt5s Harddrive Mn/jt5s Throttle Slide Vacuum Membrane For 1990-2006 Harley Davidson Flstf Hq

( Brand: Harddrive ), ( Manufacturer Part Number: MN/JT5S ), ( Compatible Year: 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 ), ( Compatible Make: Harley Davidson ), ( Compatible Model: Flstf Fat Boy ), ( Bundle Description: 1 Pc Genuine Harddrive Throttle Slide Vacuum Membrane ), ( Type: Throttle Slide Vacuum Membrane ), ( Core Charge: Free No Core Charge ), ( Fitment Type: Direct Replacement )

Review HARDDRIVE Mn/jt5s Throttle Slide Vacuum Membrane Harley Davidson Hq fits FLSTF 1990–2006

The **MN/JT5S Throttle Slide Vacuum Membrane** is a precision-engineered replacement part designed exclusively for the **1990 2006 Harley-Davidson FLSTF and FLSTFHQ** models, ensuring optimal throttle response and smooth operation for these iconic big-twin engines. Crafted from high-quality, durable materials, this vacuum membrane is engineered to replace the stock component, which can degrade over time due to heat, oil contamination, or general wear, leading to sluggish throttle action, erratic RPM fluctuations, or even complete failure of the throttle slide mechanism. The JT5S membrane features a **tightly sealed, flexible diaphragm** that maintains consistent vacuum pressure, allowing the throttle slide to move smoothly and responsively under all riding conditions whether cruising on the highway, accelerating from a stop, or handling sudden power demands. Unlike generic aftermarket alternatives, this part is **directly compatible** with the Harley s stock throttle body setup, ensuring a perfect fit without the need for modifications or additional adapters. Its **reinforced construction** resists oil and heat buildup, reducing the risk of premature failure and extending the lifespan of the throttle slide assembly. Whether you're restoring a classic FLSTF to its original glory or maintaining a well-loved ride, the MN/JT5S vacuum membrane delivers the reliability and performance expected from a Harley-Davidson, ensuring a seamless, effortless throttle experience for years to come.

**Pros and Cons of buying a HardDrive MN/JT5S Throttle Slide Vacuum Membrane for a 1990-2006 Harley-Davidson FLSTF/HQ**

### **Pros**

1. **Improved Throttle Response** The JT5S throttle slide is designed to provide smoother and more precise throttle control, reducing lag and improving overall engine responsiveness. This is particularly noticeable in stop-and-go traffic or when accelerating from a stop.

2. **Enhanced Fuel Efficiency** The vacuum membrane system helps maintain a more consistent vacuum level, which can lead to better fuel atomization and combustion efficiency. This may result in slightly improved mileage, especially in older engines prone to vacuum leaks.

3. **Reduced Throttle Sticking** Over time, stock throttle slides can develop carbon buildup or wear, causing sticking. The JT5S is a high-quality aftermarket part that minimizes this risk, ensuring smoother operation.

4. **Compatibility with Performance Mods** If you ve installed a performance exhaust, air intake, or ECU tune, the JT5S can help optimize throttle response to complement these upgrades. It works well with aftermarket carburetors (like Holley or Edelbrock) or fuel-injected systems.

5. **Durability and Longevity** HardDrive and JT5S are reputable brands known for producing durable throttle slides that outlast stock components, reducing the need for frequent replacements.

6. **Easier Installation** The JT5S is a direct drop-in replacement for the stock throttle slide, requiring minimal modification. Installation typically involves removing the carburetor, replacing the slide, and reassembling no major disassembly is needed.

7. **Better Cold-Start Performance** Some riders report improved cold-weather starting and warm-up characteristics due to the throttle slide s design, which helps maintain consistent vacuum during initial engine operation.

8. **Mainstream Aftermarket Support** Both HardDrive and JT5S are well-supported in the Harley-Davidson aftermarket. Parts, installation guides, and tuning adjustments are widely available, making troubleshooting easier.

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### **Cons**

1. **Cost** The JT5S throttle slide is a premium aftermarket part, often priced significantly higher than an OEM replacement. For a 1990-2006 FLSTF/HQ, the cost can range from **$100 to $200**, depending on the retailer and whether additional components (like a new carburetor or vacuum lines) are needed.

2. **Potential Tuning Required** While the JT5S improves throttle response, some riders may need to adjust their carburetor settings (jet sizes, vacuum ports) or ECU maps (if equipped) to optimize performance. Improper tuning can lead to rough idling, hesitation, or poor fuel economy.

3. **Mixed Reviews on Stock vs. Upgraded Performance** Some riders report that the gains in throttle response are subtle, especially if the engine is already in good condition. Others with heavily modified or high-mileage bikes see more noticeable improvements.

4. **Installation Complexity (If Combining with Other Mods)** If you re also upgrading the carburetor, vacuum hoses, or ECU, the installation process becomes more involved. This may require additional time, tools, or professional help, adding to the overall cost.

5. **Not a Cure for Underlying Issues** If your bike has vacuum leaks, a failing carburetor, or a worn-out engine, replacing just the throttle slide won t fully resolve performance problems. A comprehensive tune-up or rebuild may still be necessary.

6. **Limited Long-Term Data on Aging Engines** While the JT5S is durable, very old Harley engines (pre-2000) may have additional wear (e.g., worn camshafts, valve train issues) that could still affect throttle response regardless of the slide.

7. **Potential for Overkill on Stock Bikes** If your FLSTF/HQ is running stock with minimal modifications, the JT5S may offer marginal benefits. In such cases, a simpler solution (like cleaning the carburetor or replacing vacuum hoses) might suffice.

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### **Conclusion**

The **HardDrive MN/JT5S throttle slide vacuum membrane is a solid upgrade** for a 1990-2006 Harley-Davidson FLSTF/HQ, particularly if you re experiencing throttle lag, sticking, or poor cold-start performance. It offers **noticeable improvements in throttle response, fuel efficiency, and reliability**, making it a worthwhile investment for riders who prioritize smooth operation and potential performance gains.

However, it is **not a magic fix** it works best when paired with a well-maintained engine, properly tuned carburetor, and clean vacuum system. If your bike has other underlying issues (e.g., worn internals, carburetor problems), addressing those first may yield better results.

For **stock or lightly modified bikes**, the JT5S provides **real but modest improvements** that justify the cost. For **highly modified or performance-oriented bikes**, it can be a **key component in optimizing throttle control**, especially when used with aftermarket carbs or ECU tuning.

---

### **Recommendation**

- **Buy the JT5S if:**

- You re experiencing **throttle sticking, lag, or rough idling**.

- You ve installed **aftermarket carbs, exhaust, or an ECU tune** and need better throttle response.

- You want a **durable, high-quality replacement** for your stock throttle slide.

- You re willing to **invest in tuning adjustments** (carburetor or ECU) to maximize benefits.

- **Skip or Reconsider if:**

- Your bike is **stock with no major mods**, and you re unsure if the improvements will be noticeable.

- You have **vacuum leaks, a failing carburetor, or other engine issues** that need addressing first.

- You re on a **tight budget**, as the cost may not be justified for minimal gains.

- You prefer **simpler, lower-cost fixes** (e.g., cleaning the carburetor, replacing vacuum hoses).

**Final Verdict:** The JT5S is a **strong upgrade** for riders who want smoother throttle operation and are willing to invest in tuning. For most 1990-2006 FLSTF/HQ owners, the benefits outweigh the drawbacks, making it a **recommended purchase** especially if you re already modifying other components. However, prioritize a **full engine tune-up** before installation for the best results.

Details:

HardDrive Throttle Slide Vacuum Membrane for 1990 - 2006 Harley Davidson FLSTF hq: Status: In Stock.

part #: mnjt5s price

  • $27.22

specifications intakefuelmotorcycle:

  • for models: Flstf
  • for makes: Harley, Davidson
  • for years: 1990-2006
  • brand: Harddrive
  • mpn: Mn/jt5s
  • compatible year: 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994
  • compatible make: Harley Davidson
  • compatible model: Flstf Fat Boy
  • bundle description: 1 Pc Genuine Harddrive Throttle Slide Vacuum Membrane
  • type: Throttle Slide Vacuum Membrane
  • core charge: Free No Core Charge
  • fitment type: Direct Replacement

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  • quantity: 1
  • started: May 28, 2026
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general intakefuelmotorcycle:

  • Motorcycle Scooter Parts Accessories > Air Intake Fuel Delivery > Other Air Intake Fuel Delivery
  • condition: New
for models: flstf, for makes: harley, davidson, for years: 1990-2006, compatible year: 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994, compatible make: harley davidson, compatible model: flstf fat boy, bundle description: 1 pc genuine harddrive throttle slide vacuum membrane, type: throttle slide vacuum membrane, core charge: free no core charge, fitment type: direct replacement,
category: motorcycle parts > motorcycle scooter parts accessories > air intake fuel delivery, sku: 24097546129573813,
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