Harley Carburetor Tuning 101: The 88 Sportster Needle

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Harley tuners, mechanics, and those doing their own wrenching have long known about using the 1988 Sportster needle for tuning the Harley CV carburetor.

Harley CV Carburetor

Harley Davidson motorcycles have a long history of carburetors used on their models over the years, but none as popular as the CV carburetor. Introduced in 1988 on Sportster models to replace the Keihin "butterfly" carburetor, the CV also from Keihin introduced a vacuum actuated slide and needle to regulate fuel delivery. As engine loads change the slide moves up or down allowing the suspended needle to meter fuel passing around it from a nozzle (needle jet). This innovative fuel metering system not only handles the air/fuel mixture throughout the mid range, but also provides a constantly changing venturi or throat size, hence the name CV or constant velocity.

The original CV carburetor in 1988 lacked an accelerator pump commonly used on most carburetors. To compensate for the lack of an accelerator pump and to eliminate lean flat spots, the factory produced the N65C needle whose length, diameter, and taper positions were designed to alleviate the off idle hesitation.

In 1989 an accelerator pump was added to the CV carburetor as all other models began to adopt the new carburetor, and the CV carb remained virtually unchanged until retired in 2006. The 88 needle (or N65C, HD #27094-88) became very popular after tuners and mechanics discovered its usefulness in tuning other models needing a richer off-idle and mid range mixture required with exhaust or intake upgrades. The N65C became a staple for tuners and is still used today even by Harley dealerships. Similar needles pulled from Buell variations and other special uses were used such as the N65B, NOKK, and NOKT however the N65C remained the most popular.

The 88 Needle Lives Again
Shortly after Harley Davidson discontinued use of the CV carburetor on factory models in 2006, the factory began discontinuing older components including the N65C needle. Having insight into these parts becoming obsolete, CV Performance began producing our own N65C "Sportster" needle (fits Big Twins too) to meet the needs of those wanting to continue using them. Based on the original specs from Keihin, the N65 needle was added to our line of velocity needles using our unique precision CNC machining process and billet aluminum material.

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