Keihn needle question

[PNWrider]

Which part of the keihn needle jet has the greatest effect?

I would assume it would go in order of the letters; diameter, length, taper

But could someone verify this for me

Thanks

[PNWrider]

Effect meaning which would lean or richen or lean it the most

[Jerry Hall]

Every letter is VERY important.  Having any letter wrong on the needle can cause the engine to run rich or lean at the throttle position that the needle is controlling the fuel flow.  You can have the right pilot and main jet and still foul a spark plug or burn the exhaust side of the piston off if one of the letters is wrong for your engine set up.