lean is when there is to much air or not enough fuel, rich is too much fuel or not enough air. some of the chokes work differently. on the 400ex, when you turn the choke on your giving the bike the same amount of fuel but much much less air, making the mixture richer (good for starting). when the choke is on partially, your still giving the bike the same amount of fuel but not as much air. this is rich not lean. however, at idle, you won't notice if the choke is on half or not on at all with the 400exs. so yes, more air is needed but that means it needs to be leaned out from the rich condition. at full choke, the bike won't even idle when warm because it is way too rich.

 

Oh damn, their goes my whole theory.lol oh well, it hasn’t backfired since so I guess its fine are u sure the choke adds more gas and not air? I’m not doubt you I’m just wondering why I thought so

 

some of the chokes work differently. however, they either add more gas or limit the amount of air. this shoves more fuel in, making it richer, which is great when the bike is cold. this enables the bike to start easier.