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EC .010 Inlet Spring Shim 10 Pack
713 .020" Inlet Spring Shim (Pack of 10)
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EC .010 Inlet Spring Shim 10 Pack

Part Number: 713-SHIM
Online Price: $3.75
.010" Carburetor Inlet Spring Shims – Precision Pop-Off Tuning for Diaphragm Carbs (Pack of 10)
Availability: In Stock.

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Description

.010" Inlet Spring Shims for Diaphragm Carburetors – Precision Pop-Off Tuning


Fine-tune your carburetor performance with .010" Inlet Spring Shims, designed specifically for diaphragm-style carburetors commonly used in small engines, kart racing, and high-performance applications.


These precision shims are installed beneath the inlet tension spring, allowing micro-adjustments to the pop-off pressure by changing the spring’s installed height. Increasing the spring height raises the pop-off pressure, which helps regulate fuel volume at low engine speeds and impacts cold starting performance.


While not a direct adjustment to fuel pressure, pop-off tuning with shims gives you greater control over fuel delivery and engine responsiveness, especially when dialing in for competition or variable atmospheric conditions.


Key Features:

  • .010" Thickness for precision control of pop-off pressure
  • Used under the inlet needle spring to increase spring preload
  • Raises Pop-Off Pressure by adjusting spring install height
  • Improves Low-Speed Fuel Control & Cold Start Behavior
  • Essential for Dialing in Performance Carburetors (e.g., Tillotson, Walbro, or similar)
  • Perfect for Kart Racers, Tuners, and Engine Builders


What is Pop-Off Pressure?

Pop-off pressure is the amount of pressure required to unseat the inlet needle in diaphragm carburetors. It directly impacts how much fuel is delivered at low RPM, and influences idle quality, throttle response, and starting ease. Proper adjustment is critical for competitive tuning and consistent engine behavior.

FAQ

Q1: How do these shims affect pop-off pressure?
A: The shim increases the preload on the inlet needle spring by raising its installed height. This raises the pop-off pressure, improving fuel control at low RPMs.


Q2: Will this change fuel pressure?
A: No. These shims do not alter actual fuel pressure, but they do affect the pop-off behavior, which impacts how and when fuel enters the carburetor at low throttle settings.


Q3: What carburetors are these compatible with?
A: These are commonly used with diaphragm carburetors such as Tillotson, Walbro, and other similar performance carbs found on small engines, especially in karting and 2-cycle racing.


Q4: Can this help with hard cold starts?
A: Yes. Adjusting pop-off pressure can significantly affect cold starting ease, especially if your engine is lean or sluggish during initial startup.

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