YZ400/426/450 User Jetting Database

JETTING INFORMATION: Having a jetting problem, or think your bike is a little off? Search the links below for jetting used by TT members on the same year model of bike you ride at the same altitudes you ride. If your jetting works for you, post it there to help others.

READ BEFORE POSTING!: These threads are intended to be used as a reference collection of jetting used by members ONLY. Please use the provided template below, and post only the jetting you currently use, along with any pertinent comments. Post only in the correct thread for your model bike.

DO NOT ask questions or discuss the information posted here in this forum. If you want to talk about anything here, please do so in a new or current thread on the topic and use a link to the particular post you wish to discuss. Posts not complying with this format will be removed without comment.

NOTICE:The people who post here are of all skill levels. This information is only intended to let you see what others are using, and cannot be taken to mean that the information is accurate, will apply to your use correctly, or even that the poster's bike runs right with the posted setup. Use it as a guide/starting point only, and look at as many relevant postings as you can before proceeding.

There are a number of different YZF models, built differently, sometimes even with different carbs. What works on an '03 YZ450 will have no application to an '07, or to a '99 YZ400. To make it simpler to access information specific to your motorcycle, the jetting thread has now been divided into separate threads (links below). Old posts from the original have been transferred. PLEASE POST INFO IN THE CORRECT THREAD FOR YOUR YEAR/MODEL.

Post your jetting using the template below (copy and paste to your post) and please be as complete as you can. In the Comments section please include any modifications you feel will have a bearing on the jetting, such as cams, accelerator pump mods, bored carbs, etc., and how well you think it runs with the setup.



Edit Revision Date:

Main Jet:

Pilot Jet:

Starter Jet:

Leak Jet (if any):

Fuel screw/Setting:




Altitude Range:

Temp Range:

Humidity Range:



Post in the appropriate thread:

1998-99 YZ400

2000-02 YZ426

2003-05 YZ450

2006-07 YZ450*

2008-09 YZ450*

* '06, '07, and '08 models each seem to jet out differently. Use info for the correct year whenever possible.

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