I have my new 400s running really well now,I have the stage1 intake cam"not degreed"full yoshi system,3x3,with DJ spring & needle.My setup is 157.5 on the main,22.5 pilot"which is stock"needle 4th from the top,and fuel screw 31/2 turns out.Pretty happy with the way it runs right now,but it does have a noticable stumble at low rpm's.Mainly 2n and 3rd gear,if you let the revs get below a certain rpm...almost idle lets say and you wik the throttle open it will stumble and then hit pretty darn hard.Now if the revs dont get under that certain rpm and you wik it,it will easily loft the tire in 2nd and 3rd gear.

Ive played with the mixture screw but I dont get really any noticable results out of it.I know a good many people with this setup have gone to the 25 pilot jet,thats the only thing I havent tried,what do you coon tune gurus think?Change the pilot or not?I do appreciate ya'lls time too fellas

Bueller,Bueller

When trying to determin the pilot jetting, I prefer to use the fuel screw.

If you can turn the fuel screw all the way in without killing the engine then you need a smaller pilot jet.

If you need to keep the screw more than 3 full turns out then you need a larger pilot jet.