Keep the 140 for right now.
That 1/4-1/2 (and probably up to 3/4) flat spot, indicates that you need to richen up your midrange, which is controlled by the needle.
Basically, you are going to pull the black top cover of your carb and raise the needle jet. There are two types of carbs for our bikes. Some of them have a little clamping circling that you will simply move down one or two notches on the needle. The other kind requires that you add some tiny little washers to raise the needle. Either way, it's pretty easy.
Pull the diaphragm cover and see which kind you have. If you have the kind where you have to raise it yourself, then swing over to the home depot and get some little washers, IIRC, they were size #6 #8. Just really thin machine washers.
Follow this link for some more help:
viewtopic.php?f=8&t=15&hilit=raise+your+needle
Here is a photo of my 2006 needle:
