Using the Kawasaki to Keihin Conversion Table and plugging those values into the Keihin's  Profile Table we can determine we are looking at a needle with a 1 degree 15 minute taper, a 2.745 mm straight section diameter and a 39.95mm L1 measurement. If we look at the conversion chart you can see the equivalent Keihin part number is N427-48BGQ. Remember the Kawasaki code and Keihin's part number are not in the same order.  

This chart will work for 1988 to 2001 KDXs equipped with a Keihin PWK Carburetor. For those who own KDXs built before 1988 the parts and function of your jet needles will be the same but the conversion chart isn’t going to work for you. Sorry

Kawasaki to Keihin Conversion Table

Profile Table

Keihin Part number N-427-48_ (taper)_ (L1)_(diameter)

Here’s where things can get tricky . . . Kawasaki uses proprietary needle profiles.  Keihin won’t be able to supply a direct replacement for most Kawasaki needles. In this case they do but if you were looking for an R1173L ( 97 to 01 KDX220 ) you’d see there is no direct replacement for a needle with an " L" L1 measurement on the conversion table. Not every needle is available from Kawasaki or Keihin so you’ll need to reference both charts and make you decision based on what is available.

Common Kawasaki supplied KDX needles include:

Stock jet needle in RED

Applicable Keihin jet needles are listed here.   Needles with diameters less than 2.665 or greater than 2.745 were omitted and so were needles with a taper greater than 2° .  These profiles aren't applicable to KDX owners.

Keihin N427-48??? Series Jet Needles

TAPER

Understanding Jet Needles:

Remember that no throttle range is independent of the others. When adjusting specific throttle ranges its important to remember that there are a number of parts working together to deliver a measured amount of fuel. It’s therefore important to make one change at a time and test the result when ever possible.

The straight section – has the most effect between 1/8 and 1/4 throttle where the transition is made between the pilot/slow circuit to the main circuit. If this range is too rich a needle with a leaner/ larger straight section diameter may be required. If the range is too lean a needle with a richer/smaller straight section diameter may be required.

L1 length – The L1 measurement is normally changed by increasing or decreasing the length of the straight section, I’ve never seen it done any other way, but then again I certainly haven’t seen every available needle either. Changing to a needle with a longer or shorter L1 measurement effectively lowers or raises the jet needle in the needle jet. If your jetting is rich from 1/4 to 3/4 throttle you can either lower the needle by raising the clip position or go to a needle with a longer L1 measurement. The opposite is true for a lean condition.

1. Your present needle doesn’t have enough adjustment, i.e. you’re in the highest or lowest clip position to properly calibrate your jetting.

When changing to a needle with a different L1 measurement remember there is 0.9mm between each clip position and that the L1 measurement is taken from the top of the first (#1) clip position. If you are in the #5 (richest) clip position of a needle with a 39.95 mm L1 measurement (G) the effective L1 length of your needle is the original L1 length minus the distance from the top of the #1 clip position to the #5 clip position or.

39.95mm – 0.9mm x 4 = 36.35mm

As a general rule of thumb you should attempt to select a needle that allows you maximum adjustment.

A) If at 1/2 throttle the jetting was close in the #5 clip position and you’d like to be in the mid clip position when properly calibrated then . . . . knowing the effective L1 measurement of your needle in the #5 clip position was 36.35mm and you need to richen the circuit further you would likely go to an L1 = E or 38.15mm (BEQ). Why? In the #5 position the original needle has an effective L1 measurement of 36.35mm. If you need to change needle and want to maximize adjustment, i.e. start in the mid clip position, then 36.35mm + 0.9mm x 2 (two clip positions to #1) is 38.15mm

B) If at 1/2 throttle the jetting was excessively rich in the #5 clip position then . . . . knowing the effective L1 measurement in the #5 position was 36.35mm and you expect you’ll need to adjust the needle more than 0.9mm, one clip position, you’d likely go with a L1 of C (36.35mm). That will allow you to start in the #1 position (equal to #5 with an L1= C or a BCQ) and continue to lean the needle from there.

2. Fine Tuning -Your BGQ is too rich at 1/2 throttle in its present position (#4) but leaning the needle one position (to #3) causes the engine to run lean. In this case you can choose a needle with an L1 measurement between the two. Adding half a clip position length or 0.45mm to your BGH results in a GHH (39.95mm + 0.45mm = 40.40mm).

Just a note here you can place a 0.4 to 0.5 mm spacer under the needles clip to make fine adjustments rather that going through the expense of buying a new needle.

Jet Needle Taper – Taper changes are made to " rebalance" fuel delivery between 1/4 and 3/4 throttle.

Changes in taper are not normally required unless major physical changes have been made to the carburetor or to the engine.

Shopping - Popular carburetor resellers include Carburetor Parts Warehouse and Sudco Racing .   Both supply factory Keihin parts.  Sudco also supplies a line of less expensive brass jet needles.  Either is likely a less expensive alternative to dealer parts and have a wide variety of needle profiles available.

If you would like to use or link to this material please contact me.

If you have any comments or suggestions smack the email icon and send them my way.

  David