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Tillotson 43-988 High Speed Mixture Screw .115
43-988 Tillotson Idle Mixture Screw
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Tillotson 43-988 High Speed Mixture Screw .115

Part Number: 43-988
Online Price: $9.99
43-988 Tillotson Brass .115 High-Speed Mixture Screw – Methanol Carb Tuning
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Description

43-988 Tillotson Brass High-Speed Mixture Screw (.115) – For Methanol Open Kart Racing


The 43-988 Tillotson High-Speed Mixture Screw is a precision brass adjustment needle designed to control fuel delivery to the high-speed circuit of your Tillotson carburetor. With a .115 tip, this screw is engineered for methanol-fueled open carburetors, commonly used in high-performance kart racing setups.


This screw governs the amount of fuel delivered to the high-side nozzle or orifice, which directly impacts engine performance at peak RPM. Proper tuning of the high side is typically done on the longest straight of the track at wide-open throttle, making this component critical for optimal top-end power and throttle response.


Key Features:

  • Brass high-speed mixture screw for methanol carburetors
  • Controls fuel flow to the high-speed circuit (main jet area)
  • Ideal for wide-open throttle tuning and top-end RPM
  • Precision-machined with a .115 tip for consistent metering
  • Specifically built for open-class kart racing


Tuning Tip:

Tune your high-speed needle at full throttle on the longest part of the track to avoid running too lean or too rich at peak engine load. A properly set high-side screw ensures maximum power and safe engine temps.


Specifications:

  • Material: Brass
  • Tip Size: .115
  • Part Number: 43-988
  • Adjustment Range: High-speed (main circuit)


Fits the Following Tillotson Carburetors:

  • HL-293F
  • HL-355A, HL-355B, HL-355C, HL-355D, HL-355E
  • HL-360B, HL-360C
  • HL-363C
  • HL-380A, HL-380B

Always confirm compatibility with your carb model and check for tuning limitations before installation.

FAQ

What does the 43-988 high-speed mixture screw do?

It controls fuel flow to the high-speed circuit of your Tillotson carburetor. This circuit is tuned for peak RPM and wide-open throttle performance.


What carburetors is the 43-988 screw compatible with?

It fits several Tillotson HL-series methanol-compatible carburetors including:

  • HL-293F
  • HL-355A–E
  • HL-360B, HL-360C
  • HL-363C
  • HL-380A, HL-380B


When should I adjust the high-speed mixture screw?

Tune the high-speed screw at wide-open throttle—typically on the longest straight of the track. This ensures the engine receives the correct fuel volume under maximum load.


Is the 43-988 screw made for methanol carbs?

Yes. It’s commonly used in methanol-fueled open-class kart racing carburetors, where precise high-speed fuel control is critical for performance.


What is the tip size of this screw?

The tip measures .115, which determines the volume of fuel delivered at high RPMs. A larger tip allows more fuel, ideal for high-output engines.

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