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Idle Mixture Screw Spring for Honda GX390 & Big Block Clone Carburetors
188F-37 GX390/420 Clone Idle Adjuster Screw
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Idle Mixture Screw Spring for Honda GX390 & Big Block Clone Carburetors

Part Number: 188F-37
Online Price: $0.99
Idle Mixture Screw Spring – Fits GX390 & Big Block Clone Carburetors
Availability: Out of Stock.

Description

Idle Mixture Screw Spring for Honda GX390, Predator 420 & Big Block Clone Carburetors


This idle mixture screw spring is a small but essential component in the carburetor of most Honda GX390-style and Big Block Clone engines, including Predator 420 and Wildcat 460.


The spring provides consistent tension on the idle mixture screw, keeping it locked in place to prevent vibration-related fuel adjustments or the screw backing out during operation. This helps maintain stable idle RPMs and precise low-speed fuel metering, which is especially important for performance tuning and engine reliability.


Ideal for carburetor rebuilds or when installing a new idle mixture screw.


Key Features:

  • Keeps idle mixture screw in correct position under vibration
  • Prevents the screw from loosening or backing out
  • Ensures consistent low-speed fuel metering
  • OEM-style fit for stock GX390-style carburetors
  • Perfect for tuning, rebuilding, or replacing lost/damaged springs


Compatibility:

  • Honda GX390
  • Predator 420
  • Wildcat 460
  • Most GX390-style clone carburetors with adjustable idle mixture screws

Note: Many modern carburetors no longer include idle mixture screws due to emissions restrictions. Make sure your carb has an adjustable screw before ordering.

FAQ

Q1: What does the idle mixture screw spring do?
A: The spring maintains tension on the idle mixture screw, preventing it from loosening due to engine vibration and helping maintain consistent low-speed fuel delivery.


Q2: How do I know if I need a new one?
A: If your idle screw won’t hold position, keeps backing out, or you’re doing a carb rebuild and can’t locate the original spring, it’s time for a replacement.


Q3: Is this spring compatible with all GX390-style carburetors?
A: It fits most OEM-style and Ruixing clone carburetors that have an adjustable idle mixture screw. Not all carburetors include that feature due to EPA restrictions.


Q4: Can I install this spring without removing the carburetor?
A: Yes, in most cases you can install or replace the spring by simply removing the idle screw—no need to fully remove the carburetor from the engine.


Q5: Does this come with the idle mixture screw?
A: No, this listing is for the spring only. The idle mixture screw is sold separately.

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