i am posting for a friend.
'06 400ex with full yoshi rs3 exhaust and no airbox lid, elevation 1000 feet.
i need a ballpark suggestion to jet this thing, i am not farmiliar with 400ex's and do not know where to begin jetting wise, trying to search the forum didnt give any answers. he doesnt want to buy a complete jet kit he just wants to buy a few assorted jets from the shop. hopefully someone has a similar setup and can give me a suggestion, i can fine tune from there. thanks in advance, no dynojet numbers please!

 

on my 400ex with just a slip on pipe and no air box lid 178 was not enough and 195 was to much.

 

Start around 42 slow jet and a 160main that should be a good starting point