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  1. Trx400ex issue

    Maintenance / Important Information
    i bought a 2008 trx400ex a week ago it has a new 440cc big bore that the guy installed, i still have the stock bore which is in good condition and pistons. The upgrades i have are the big bore an hmf slip on and that all that i know of airbox is still on i dont know if the quad has been jetted i...
  2. 400ex tuning problems

    Engine/EFI/Drivetrain
    I need opinions on my tuning: I've got a 2000 400ex, original motor, wrapped header, oil change. Rebuilt the carb and adjusted valves. After a lot of trouble with backfiring through the carb (signifying really lean) I'm running a 42 pilot jet and a 150 main jet. This helped a lot, but I'm still...
  3. 400ex re jetting help

    Site Issues, Bug Reports & Suggestions
    Hi I just rejetted my bike today with the dynojet kit. I have an 02 400ex with a 440 big bore kit, big gun full exhaust, and moose air filter with no lid. I used a size 42 pilot jet and 170 main jet which is the size that the kit recommended. I also changed the needle to the one that came with...
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