I'd try the 140 lower than that sounds too small though I've never fiddled with 2 strokes (I run 100's on my 28mm carbs (4 stroke twin)). A lot of it is trial and error so it's a good idea to have a few sets of jets of neighbouring sizes. It took me a lot of fiddling (and hours of cursing) to get mine right when I replaced the airbox with a pair of proper cones, infact the thought of having to go through it again is the reason I'm no longer planning on getting better pipes.