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Tillotson 363-501 Nozzle Check Valve
363-501 Tillotson Nozzle Check Valve
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Tillotson 363-501 Nozzle Check Valve

Part Number: 363-501
Online Price: $9.99
Tillotson 363-501 Press-In Nozzle Check Valve for HL-Series Carburetors
Availability: In Stock.

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Description

Tillotson 363-501 OEM Nozzle Check Valve – Press-In Style for HL-Series Carburetors


The Tillotson 363-501 Nozzle Check Valve is a precision-engineered, OEM replacement part designed to protect the internal fuel circuits of your carburetor during a backfire event. It features an integrated check ball that automatically seals the fuel passage, preventing reverse pressure from causing internal damage.


While the physical length and shape of the nozzle can have minor effects on fuel signal and tuning behavior, the check ball itself is not a tuning device—its sole purpose is safety.


Key Features:

  • OEM Part Number: 363-501
  • Design: Press-in brass nozzle with internal check ball
  • Function: Seals fuel circuit during backfire to prevent internal carb damage
  • Nozzle Dimensions:
    • Length: 0.352 inches
    • Diameter: 0.250 inches
  • Material: Durable brass construction for corrosion resistance and longevity


Important Installation Notes:

  • This is a press-in style nozzle. Some Tillotson carbs use threaded nozzles—confirm your model before attempting installation or removal.
  • Always remove the high-speed adjustment screw before installation to prevent damage to the needle.
  • When reinstalling, make sure the side hole of the nozzle aligns with the pick-off hole—this ensures proper fuel flow and carburetor performance.
  • Misalignment can cause poor tuning, hard starts, or inconsistent performance.


Troubleshooting Tip:

If your carburetor is leaking fuel from the high side at idle, the check valve is not likely the issue. This is commonly caused by a leaking needle valve or worn seat, not by the nozzle or check ball.


Compatible Tillotson HL Carburetor Models:

The 363-501 fits a wide range of Tillotson HL-series carburetors, including but not limited to:
HL-63G, HL-108A, HL-158A, HL-166B, HL-173A, HL-212A, HL-222A, HL-222B, HL-227A, HL-227E, HL-229A, HL-229E, HL-231B, HL-231E, HL-232A, HL-232E, HL-239B, HL-239BE, HL-239E, HL-244A, HL-250A, HL-253A, HL-255A, HL-260A, HL-261A, HL-274A, HL-274E, HL-276A, HL-284A, HL-287B, HL-292B, HL-292G, HL-294A, HL-296A, HL-296E, HL-301A, HL-301E, HL-306B, HL-319A, HL-322A, HL-322E, HL-324A, HL-326A


Fitment Tip:

If your model is not listed, measure your existing nozzle to confirm compatibility. Length and diameter must match (0.352" x 0.250").

FAQ

Q1: What does the Tillotson 363-501 nozzle check valve do?

A: The 363-501 check valve protects your HL-series carburetor from backfire damage. It uses a built-in check ball to seal the fuel passage and prevent reverse pressure from reaching internal circuits.


Q2: Is this a tuning component?

A: No. While the nozzle’s shape and size can affect fuel signal slightly, the check ball is a safety mechanism, not a tuning feature.


Q3: Is the 363-501 nozzle press-in or threaded?

A: This part is a press-in style nozzle. Do not attempt to install it into a carburetor that uses a threaded nozzle.


Q4: I’m seeing fuel leak from the high side at idle. Is the check valve the cause?

A: Unlikely. Most high-side fuel leaks are caused by a worn or leaking needle valve or seat, not by the nozzle check valve.


Q5: How do I install the nozzle correctly?

A:

  • Remove the high-speed screw before removing or installing the nozzle.
  • Make sure to align the nozzle’s side hole with the pick-off hole inside the carburetor.
  • Improper alignment may result in tuning and performance issues.


Q6: Which carburetors are compatible with the 363-501 nozzle?

A: It fits many HL-series Tillotson carburetors, including models like HL-63G, HL-108A, HL-158A, HL-232A, HL-239B, HL-284A, HL-296A, and dozens more. Always verify model number or match dimensions (0.352" x 0.250") before ordering.

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