1999 yz400 carb schematic?

2 replies to this topic
  • BrokeLoser

Posted March 19, 2011 - 05:16 PM


Hello all...noob here.
I acquired a 1999 yz400 for a steal but of course it has 'carb issues' from sitting so long.
I pulled the carb off and now I'm about to start tearing into the float bowl.
Dumb question:l
I've never had one of these apart; can someone tell me where the jets are located and which ones I need to replace?
Pilot jet?
Leak jet?
Main jet?
Also, I think I read somewhere that I should count the number of turns out the pilot jet is?
Isn't the pilot in a fixed position? All the way in?

Thanks...much appreciated!

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • brentn

Posted March 19, 2011 - 10:58 PM


Search for jetting, you can also search for AP pump tuning in this and the jetting forum. You can find diagrams from almost any website that sells OEM yamaha parts. Bike bandit, thumpertalk store, etc. There are also public Yamaha parts fiche's on the USA yamaha website.

  • grayracer513

Posted March 19, 2011 - 11:13 PM


Download a manual here:


The YZ400 manuals used photographs which don't reproduce well in PDF's such as these, so also download the 2000 YZ426. The carb layout is nearly identical.

Also, you are confusing the pilot jet, which is fixed and does indeed screw all the way in, with the pilot fuel mixture screw, which is adjusted about 1.75 turns out from fully seated:



Related Content


yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F

Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies

yz400f throttle bog by yz400fmaniac

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • * * * * *
  • Hot  28 replies

Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

First Hare scramble tips by dhend8

Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  33 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.