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  6. 098-090 Bully .090 Red Adult Clutch Spring
098-090 Bully .090 Red Adult Clutch Spring
098-090 Bully .090 Red Adult Clutch Spring
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098-090 Bully .090 Red Adult Clutch Spring

Part Number: 098-090
Online Price: $3.25
Bully .090 Red Clutch Spring – Senior & Box Stock Racing Kart Clutch Spring
Availability: In Stock.

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Description

Bully .090" Red Clutch Spring – High-Performance Racing Clutch Spring for Adult & Senior Classes


The Bully .090 Red Clutch Spring is the standard go-to spring for Adult or Senior Box Stock karting classes and 4-spring Junior Bully Clutches. Built for consistency and tunability, this spring delivers the optimal tension and clutch engagement for competitive racers looking to dial in their performance.


Engineered with a .090-inch wire diameter, this red spring provides a balanced engagement RPM ideal for stock to mildly modified racing engines. Easily adjustable and color-coded for convenience, it allows racers to fine-tune their clutch setup based on power band, track conditions, and driver preferences.


Key Features:

  • Designed for Senior/Adult Box Stock Classes and Junior 4-spring Bully Clutches
  • .090" Red Spring = Medium Engagement Tension (Factory default on many clutches)
  • Color-Coded Tension Ratings:
    • Blue (.100"): Higher tension for later (higher RPM) clutch engagement
    • Black (.086"): Lower tension for earlier (lower RPM) clutch engagement
  • Easily Adjustable Stall Speed – Fine-tune by rotating spring retainers
  • Engagement RPM Range: Approx. 4,900 RPM (factory default) with ability to tune between 4,700–5,700+ RPM


How Clutch Spring Tuning Works:

  • Clockwise Spring Adjustment = Increases spring preload ? Raises stall speed (more slip)
  • Counterclockwise Spring Adjustment = Reduces spring preload ? Lowers stall speed (less slip)
  • Recommended Adjustment Range: .150" – .330" spring height (distance between spring washer and activator plate)
  • Average RPM Change: ~100 RPM per ¼ turn of adjustment on all six springs(varies based on weights, levers, clutch condition)


Pro Tip: For best performance, adjust all springs equally in ¼ turn increments. Always allow clutch to fully cool between tests to prevent overheating and premature wear.

FAQ

Q1: How do I adjust the spring for a different stall speed?
A: Turn the spring retainer clockwise to increase tension (more slip/higher RPM), and counterclockwise to reduce tension (less slip/lower RPM). Make adjustments in ¼ turn increments to all six springs for best results.


Q2: Can I use this spring on a junior clutch?
A: Yes, this spring is compatible with 4-spring Junior Bully Clutches and widely used in Adult and Senior Box Stock karting classes.


Q3: What's the difference between red, black, and blue clutch springs?
A: Each color indicates the wire diameter and tension:

  • Red (.090"): Medium tension (default)
  • Blue (.100"): Higher tension, for high-RPM setups
  • Black (.086"): Lower tension, for earlier engagement


Q4: How does clutch engagement affect racing performance?
A: Proper clutch engagement ensures the clutch locks at the engine’s torque peak, delivering maximum acceleration. Adjusting spring tension allows fine-tuning of this engagement point for optimal track performance.

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