wr 400 with 426 carb starting problems

2 replies to this topic
  • ShmUDE

Posted January 14, 2008 - 07:31 PM


It will not start without the hot start pulled out. Im pretty sure the bike is running too rich and i should go down in the Pilot Jet, but i already did that...down to a 38. Should i go lower? I think it only goes down to a 36 or could i make the pilot air jet larger? Its a 75 right now.

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  • fadingfastsd

Posted February 16, 2008 - 01:37 PM


I have a 99 WR400, and I just swapped to a 2001 WR426 carb.
I'm having the exact same problem! What the hell? The thing will only start with the hot start on. I plugged the vacuum nob at the intake.

Any ideas??

  • tcmII

Posted February 18, 2008 - 07:04 PM


This will sound crazy if you don't understand carb theory, but a stock jetted card for a 426 should be too lean for a 400.

All things being the same except displacement, the larger displacement will draw more are through the carb createing more vacuum, and draw more fuel through the same jet.

Stock yz426 uses 162 main, stock needle on 4 and 42 pilot
Stock wr400 (98) uses 168 main, stock needle on 3 and 45 pilot

You should check your feul screw and float setting, both will also make you very rich at idle.

Just some thoughts, hope they help.


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