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  5. EC .005 Inlet Spring Shim 10 Pack
EC .005 Inlet Spring Shim 10 Pack
712 .005" Inlet Spring Shim (Pack of 10)
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EC .005 Inlet Spring Shim 10 Pack

Part Number: 712-SHIM
Online Price: $3.75
.005" Carburetor Inlet Spring Shims – Fine Adjustment for Pop-Off Pressure (Pack of 10)
Availability: In Stock.

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Description

.005" Inlet Spring Shims for Diaphragm Carburetors – Fine-Tune Pop-Off Pressure


Optimize your carburetor's performance with .005" Inlet Spring Shims, designed for diaphragm-style carburetors used in kart racing, two-stroke engines, and other high-performance small engine applications.


These ultra-thin shims are installed beneath the inlet needle spring to make fine adjustments to pop-off pressure by slightly increasing spring preload. A subtle increase in pop-off pressure enhances fuel control at low speeds, refines idle quality, and improves cold-start reliability—without the need to replace springs.


Perfect for racers and tuners seeking precision fuel metering, these shims allow small, incremental changes to dial in your carburetor for peak performance in varying conditions.


Key Features:

  • .005" Thickness – ideal for precise, incremental tuning
  • Increases Inlet Needle Spring Preload
  • Fine-Tunes Pop-Off Pressure in Diaphragm Carburetors
  • Improves Throttle Response, Idle, and Cold Starts
  • Fits Popular Performance Carbs: Tillotson, Walbro, and more
  • Essential for High-Performance Engine Builders & Racers


What Does Pop-Off Pressure Do?

Pop-off pressure determines when the carburetor’s inlet needle opens to allow fuel into the metering chamber. Adjusting it with shims helps tune your engine’s fuel volume at idle and low RPM, impacting throttle responsiveness and starting performance.

FAQ

Q1: What does a .005" shim do compared to .010"?
A: A .005" shim provides smaller, more precise adjustments to the inlet spring tension and pop-off pressure—ideal when a .010" change would be too drastic.


Q2: Will these shims work with my carburetor?
A: These are compatible with most diaphragm-style carburetors, including Walbro, Tillotson, and other performance carbs used on racing engines, 2-cycle engines, and small engines.


Q3: How do I install these shims?
A: Simply place the shim under the inlet needle spring during reassembly. Multiple shims can be stacked to reach the desired pop-off pressure.


Q4: Can shims affect fuel delivery?
A: Yes, indirectly. By changing pop-off pressure, shims affect how easily fuel enters the carb at lower RPMs, improving control without changing the metering circuit.

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