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Tillotson 363-517 Nozzle Check Valve
363-517 Tillotson Nozzle Check Valve
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Tillotson 363-517 Nozzle Check Valve

Part Number: 363-517
Online Price: $11.99
363-517 OEM Tillotson Nozzle Check Valve for HL Series Carburetors
Availability: In Stock.

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Description

363-517 Tillotson Nozzle Check Valve – OEM Press-In Valve for HL Carburetors


The 363-517 Tillotson Nozzle Check Valve is a crucial safety component in select Tillotson HL carburetors, designed to prevent damage during a backfire event by sealing off the fuel passage with an integrated check ball mechanism.


While the nozzle's length and shape may slightly influence carburetor signal and tune, this check valve is not only a tuning component. Its main role is to protect the internal fuel circuit by stopping reverse pressure or flame from entering the carburetor body.


Key Features:

  • OEM Tillotson Part #363-517
  • Built-In Check Ball – Seals fuel passages in the event of a backfire, protecting internal components
  • Durable Brass Construction – Ensures longevity and precise fuel flow
  • Press-In Style Nozzle – Compatible with many HL-series carburetors
  • Exact Fit Dimensions:
    • Length: 0.435 inches
    • Diameter: 0.25 inches


Installation Notes:

  • Most Tillotson nozzles are press-fit, but some models use a threaded nozzle. Confirm type before removal.
  • Always remove the adjustment screw before installing the nozzle to avoid damaging the needle.
  • Align the side hole on the nozzle with the pick-off hole (where the adjustment screw draws fuel) for proper circuit function.
  • Improper alignment may cause tuning issues or poor engine performance.
  • This valve does not correct flooding at idle. If fuel leaks from the high side at idle, check for a leaking needle valve or seat, not the check valve.


Compatible Tillotson Carburetor Models:

  • HL-264B
  • HL-314A
  • HL-314E
  • HL-348D

Always consult your carburetor model number or measure the existing nozzle to ensure compatibility before ordering.


Ideal For:

  • Small engine repair shops
  • 2-cycle and karting engine tuners
  • Users restoring or rebuilding Tillotson HL carburetors
  • Replacing damaged or missing nozzle check valves

FAQ

What does the Tillotson 363-517 nozzle check valve do?

The 363-517 check valve protects your Tillotson HL carburetor from backfire damage. It uses a built-in check ball to block reverse pressure from entering the fuel passage.


Is the 363-517 check valve a tuning part?

It can. While the length and shape of the nozzle may slightly affect carburetor signal, the check ball is not used for tuning. It’s strictly a safety component.


What are the dimensions of the 363-517 nozzle?

  • Length: 0.435 inches
  • Diameter: 0.25 inches
    Always measure your existing nozzle if unsure of compatibility.


What causes high-side fuel leaks at idle?

Fuel leaking from the high side at idle is usually due to a leaking needle valve or worn seat, not the check valve. The 363-517 won’t fix this condition.


Which Tillotson carburetors use the 363-517 check valve?

This nozzle fits: HL-264B, HL-314A, HL-314E, and HL-348D. Confirm your model before installation.


How should I install the Tillotson nozzle check valve?

  • Ensure the adjustment screw is removed before installation.
  • Carefully press in the nozzle, aligning the side hole with the pick-off hole (fuel circuit).
  • Misalignment can lead to tuning or performance issues.

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