If you’re on a quest for Harley CV Carb Performance, you’re in the right place! Today we’re talking about the Jet Needle.
The jet needle is a long tapered rod that controls how much fuel can be drawn into the carburetor venturi. The thinner the taper, the richer the mixture.
The needle itself, as well as shims or an adjustment clip are used for fine tuning in between jet sizes. So, let’s say you try 2 jet sizes and experience lean issues with the smaller one, and rich issues with the larger one. A different needle, or a needle adjustment of your current one may be the answer.
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. This allows the suspended needle to meter fuel passing around it from a nozzle (needle jet). This innovative fuel metering system handles the air/fuel mixture throughout the mid range, and 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, the factory produced the N65C needle. The N65C’s length, diameter, and taper positions were designed to alleviate the off idle lean condition and hesitation.
In 1989 an accelerator pump was added to the CV carburetor. All other models began to adopt the new carburetor, and the CV carb remained virtually unchanged until retired in 2006. The 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. Especially 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 and other special models are popular, too. Jet needles such as the N65B, NOKK, and NOKT however the N65C remained the most popular.
Harley CV Carb Performance Jet Needles
In addition to the OEM N65C, N65B, NOKK, NOKT, and NOKV, there are a number of aftermarket choices. 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.
Harley CV Carb Jet Kit manufacturers like Dynojet also have their own needles that they include with the kit with varying designs.
Harley CV Carb Needle Adjustment
Brass #4 washers can be used to shim the needle to richen up the fuel curve sooner. This is great for curing lingering off-idle lean conditions, carb farts, and other common fuel-related tuning issues.
You want to use a washer around .020″ thick, so you may want to bring some calipers along with you to the local hardware store to check a few out.
Start with one washer on the needle, and test ride. Add another afterwards if you think it’ll be necessary.
If your jet needle has a clip, use that instead.
And that’s pretty much all there is to Harley CV Carb Jet Needles!