Repository containing information about parts and modifications for various motorcycles

This project is maintained by mitchellwaite

Carburetor Jet Kits and CDI tuning

< KLX 250

Ignition Tuning

The CDI modules on the carbureted KLX 250 and 300 models are non-adjustable. Timing for the 250s are set set to 10° at 1300 rpm, increasing to 25° (or 35° for Aus models) at 5000 rpm. Timing for the 1994-1996 250s and 1997-2004 300s are set to 10° at 1700rpm, increasing to 40° at 3000rpm

For stock bore 250s, messing with the timing doesn’t make much of a difference power wise. However, if something like a big bore kit is installed or the cams are changed, it may be worth it to modify the ignition map.

PaRay Electronique makes aftermarket CDI modules that replace Kawasaki P/N 21119-1579 (2006/2007), 21119-0086 (2009-2015), and 21119-1533 (2006-2020 Aus).

The comes with the stock NA and Aus maps, but it is possible to fully customize the ignition curve or change things like the rev limiter or the anti-theft features. On KLX models with a TPS, it is possible to tune ignition by rpm and throttle position. Even if you don’t want to mess with the timing, the PaRay ignition modules are quite a bit cheaper than OE Kawasaki modules if you need a new replacement.

As of March 2021, they are listed for $179 CAD (~$140 USD), while quotes from a local dealer for a replacement CDI are $460 CAD for the 2009-2014 module, or $446 CAD for the 2006-2007 module.

Simple Jet Kit

The simple jet kit applies to carbureted KLX 250S models from 2009-2014. The parts in this kit can theoretically be installed in other CVK34 based models, but performance is untested.

It can be used with a stock airbox and exhaust, but greater gains can be achieved by removing the airbox snorkel and installing an aftermarket exhaust.

Parts Needed

Brand Part No. Qty Needed Link Notes
Dynojet 2152 1  

Install the Dynojet kit as per instructions.

Simple Jet Kit for Big Bore

Full Disclosure: Unless your region has vehicle inspections where a stock intake and/or exhaust is required, the reccomentation would be to remove the airbox lid and use the “Advanced”/”Lidless” recipe shown in the next section. That will unlock the most amount of power from a big bore cylinder.

If a bigger bore cylinder is being installed with a stock intake/exhaust or with light modifications (slipon/bigger or no snorkel), ask the manufacturer for their recommendation on what jets to use in the carburetor.

A good starting point for a big bore w/ a stock intake and exhaust would be to go +1 size on the pilot jet and +2 sizes on the main jet, so 38 pilot (P/N 92064-1050) and 122 main (P/N 92063-1073). Increase jet size as needed if the snorkel is removed and/or an exhaust is installed.

The dynojet kit is useful to have, since it includes an assortment of jets and a fuel needle that is adjustable. If a big bore is installed, start with +1 jet size over the dynojet recommendation for the mods installed.

Advanced Jet Kit (a.k.a the lidless recipe)

If an aftermarket exhaust is in use, and the airbox lid is removed, the following steps will provide the best results for power with the CVK34 carburetor on a stock engine.

They can also be applied to KLX 300 models (or 250s with the 292cc cylinder from the 300), or bikes that have been fitted with a 331cc or 351cc big bore kit.

Parts Needed

Fuel Needle

Choose one of the following kits, as needed for the fuel needle

OPTION 1: Needed for the DNO228 fuel needle & washers

Brand Part No. Qty Needed Link
Dynojet 2152 1

OPTION 2: Needed for the DNO352 fuel needle & washers

Brand Part No. Qty Needed Link
Dynojet 2206 1

When installing the fuel needle, set the clip at the top-most position and superglue the two DJ washers to the top.

Main Jet

Choose an appropriate main jet based on the exhaust system:

Brand Part No. Qty Needed Link Notes
Kawasaki 92063-1331 1   152 Main Jet
Kawasaki 92063-1367 1   158 Main Jet
Dynojet   1   DJ140 Main Jet
Dynojet   1   DJ144 Main Jet
Dynojet   1   DJ146 Main Jet
Dynojet   1   DJ148 Main Jet

If individual dynojet jets/jet kits are difficult or not economical to purchase, the 1102 kit for the CRF 450R contains all jets from DJ134 to DJ150

Brand Part No. Qty Needed Link Notes
Dynojet 1102 1  

Pilot Jet

Choose an appropriate pilot jet based on elevation:

Brand Part No. Qty Needed Link Notes
Kawasaki 92064-1108 1   #40 pilot jet
Kawasaki 92064-1050 1   #38 pilot jet