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ARC 5.75 Small Billet Flywheel for Honda GX390-420-460
ARC 5.75 Small Billet Flywheel for Honda Big Block Engines
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ARC 5.75 Small Billet Flywheel for Honda GX390-420-460

Part Number: 6607-GX3
Online Price: $195.00
ARC 6607-GX3 Billet Flywheel – Ultra-Lite Adjustable Timing Flywheel for GX390 / Predator 420
Availability: In Stock.

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Description

ARC 6607-GX3 Ultra-Lite Billet Flywheel – 5-3/4” Diameter for GX390 / Predator 420 / Big Block Clones


The ARC 6607-GX3 Ultra-Lite Billet Flywheel is a precision-engineered, SFI-certified racing flywheel designed for Honda GX390, Predator 420, Wildcat 460, and other GX390-style Big Block Clone engines.


This 5-3/4" diameter CNC-machined billet aluminum flywheel offers significant performance gains over stock cast iron flywheels. Built specifically for sanctioned racing, it delivers faster response, greater spark energy, and on-the-fly timing adjustability without disassembling the engine.


Key Performance Features:

  • Ultra-Lightweight Design (3.5 lbs) – Reduces rotating mass for quicker throttle response
  • Adjustable Timing Hub – ARC’s patented steel timing hub allows 2° increments up to 14° advance
  • Quick Adjustability – Set ignition timing in 90 seconds without offset keys or teardown
  • Improved Coil Output
    • 17% increase in voltage at the coil
    • 38% overall voltage gain via the optimized Forward Curve fin design
  • Neodymium Magnet – Strongest magnet type available for accurate ignition trigger
  • Dual-Purpose Timing Hub – Also functions as a built-in flywheel puller


Technical Specs:

  • Flywheel Weight: 3.5 lbs
  • Minimum Coil Gap: .030"
  • Torque Spec: 65 ft-lbs
  • Replaceable Ring Gear: Made of 7075 billet aluminum
  • Construction: SFI-certified CNC billet aluminum


Important Compatibility Notes:

  • Not for stock charging systems – This flywheel does not support charging coils
  • Not compatible with OEM pull start or electric starters
  • Requires external handheld starter only
  • Requires ARC #5980 Coil Bracket (sold separately)
  • Use with OEM non-UT2 ignition coil for proper performance


Tuning Caution:

Advancing timing beyond safe limits may cause:

  • Pre-ignition ("engine knock")
  • Overheating
  • Exhaust valve flutter
  • Crankshaft damage

Tune conservatively and verify with proper timing tools for maximum safe power.

FAQ

Q1: What engines are compatible with the ARC 6607-GX3 flywheel?
A: This flywheel fits Honda GX390, Predator 420, Wildcat 460, and other GX390-style Big Block Clone engines. It’s designed for racing applications only.


Q2: What makes this flywheel different from the stock version?
A: The ARC 6607-GX3 is:

  • CNC-machined from billet aluminum (not cast iron)
  • Much lighter at 3.5 lbs for quicker engine response
  • Includes an adjustable timing hub with 2° increments
  • Produces stronger, cleaner spark output


Q3: Can I use this with my factory electric starter or pull rope?
A: No. This flywheel is not compatible with OEM pull starts or electric start systems. It must be used with a handheld electric starter.


Q4: Do I need any other parts to install this flywheel?
A: Yes. You’ll need the ARC #5980 billet coil bracket (sold separately) to properly position the ignition coil due to the smaller 5.75” diameter.


Q5: What kind of coil should I use?
A: Use the OEM non-UT2 ignition coil for proper spark generation. UT2-style coils are not compatible.


Q6: How do I adjust the ignition timing?
A: Simply rotate the steel timing hub in 2° increments—up to 14° of total advance—without disassembling the engine or using offset keys.


Q7: Is it safe to max out the timing advance for more power?
A: Not always. Too much ignition timing can lead to:

  • Pre-ignition (engine knock)
  • Overheating
  • Exhaust valve flutter
  • Crankshaft failure
    Always tune conservatively and test under load.

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