what size slow and main jet should be used in a 400ex w/k&n and yosh complete with air box lid on (don't want to take off or drill holes in it!) with out it running lean or rich right now i have a 50 slow and 158 main. i think i should go down on the slow cause it's running and idling good but running a little rich. any higher on the main without removing or drilling holes? any one have a 160? any and all suggestions will help. even from people with a different aftermarket exhaust. I want a general idea. I live in Pennsylvania what ever the elevation is here. Thanks guys.

 

Wicked i called yosh myself to find out what to jett my 400 at with there full system ....They told me 160 to 162 main ..Down 1 notch on needle and DONT mess slow jett...I bet that was with a k and n filteralso installed ....
hope this helps ......bigboy400ex

 

that's what they told me also but remember they are based in California and I am in Pennsylvania, different elevations. my friend has a 162 in his and has to have the lid on his air box proped open a little. i want the bigest jet i can without drilling holes or removing the lid. I have a 158 right now. 50 slow jet but black plug when checked after idle for a few min. picked up a 40 slow today and will put it and a new plug in after work. I'll let you know how it turns out. any other suggestions from any one?