400ex problem

[YFZ PILOT]

My wifes 400ex is stock, she wanted a little more power so I put a kn with outerwear and took out the baffle. My problem now is when I give it a quick rev from idle it almost dies. I put a 155 main in and messed with the air mix screw on carb. Any sugg ... thanks.

[Aceman]

Put the fuel screw back to stock, 2 1/4 turns out. If it still doesn't run right put the stock main jet back in. I have a 300ex so I don't know what size main jet is stock for a 400ex. Since your bike is pretty much stock except for the filter I doubt you even need to change the stock jetting.

[cals400ex]

yep, i would go down to a 150 keihin mainjet. it would probably not be a bad thing to just put in a 40 or 42 pilot jet now even though the bike is mostly stock. it may help with starting problems in cold weather. also, make sure the bike is 100% warmed up when you hit the throttle. if it isn't, it may not respond the best. also, make sure your choke isn't on or it will miss.