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!

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  • 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:



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