swoop,
Hopefully this post will display correctly:
http://vintagedirtbikeforums.alp-sys.com/viewtopic.php?f=21&t=3831&p=13327&hilit=oxygen&sid=05904e8d1a15d859befd361e99c1848f&sid=05904e8d1a15d859befd361e99c1848f#p13327texasmark,
You're right, the needles are definitely different. The OEM '74 needle for the 004A carb (271002) is quite rich, and Honda made succeeding needles steadily leaner all the way to the end (092B FL250 carb). The FL250 Keyster kit is the one I'd get, as its D96 needle is super lean and it's got the cool big-knob idle speed screw. I've got specs for a bunch of the Honda OEM 70's 2-stroke needles, PM me if you need 'em.
I replaced the needle & jet on my friend's '74 MT with a NOS 16012-358-034 set, it made almost no difference at all. I believe leaner slides / needles / pilot jets would really wake this bike up, but I haven't had the chance to test any of them on an MT250 (although they worked great on my MR175). Something else is going on with the MT250's carb too, as many of them overflow for no apparent reason.
Ray