[benroot]

I just bought a 2004 400ex that has a full White Brothers Exhaust. (pipe and muffler) It has all stock engine components and a stock carb and I want to run it with a closed lid on the airbox and a Two-Stage Foam Uni Air Filter. What should my jetting look like? I am new to this so any tips are appreciated. Also I am located in central to northern Michigan so my elevation where I ride is anywhere from 500ft to 1500ft.

 

[Eric the red]

40-42 pilot 152-155 main with the stock needle setting.
Stock is 38 pilot and 148 main. You dont need much bigger jets with the lid on the air box, if you take it off go up 2-3 sizes further on the main.

 

[benroot]

Thanks for the help I appreciate it! Is there a specific brand of jet you would suggest?

 

[The93ex]

Thanks for the help I appreciate it! Is there a specific brand of jet you would suggest?

I know HMF sells jet kits I would look there

 

[Eric the red]

The cheap way to buy jets is to buy keihin jets in the sizes you need, amazon or rockymountainatv has them.
You need the longest keihin pilot jet, not the short ones, all keihin hex head jets are the same tho.
You can also buy a dynojet jet kit, which is sold under a few different names, dynojets have different numbers so they will be different IE a dynojet 150 is way bigger than a kiehin 150. If you get a dynojet jet kit just follow its instructions.