Ok, to make a long story short i got screwed by buying a 250r off ebay. Origionally the bike had a stock bore of 66mm but had a 38mm carb on it (stock 34mm) which was entirely to big, the bike didnt run right at all. So i got a new 35mm for it and it ran lean to long and blew up.............
So now i got it all back together it has a CT Racing full pipe on it, Stage 2 Pro National port and polish and 76mm wiseco piston. Im having big tuning problems.
1 to start off with, air/fuel mixture 1.5 turns out. 165 main needle all the way up so it would run rich simptoms were wet plug no power at all.
2-165 main 2nd notch from bottom, plug dry black no power all around.
3-160 main 2nd notch from bottom, plug brown black around the outsides, no low end, mid breaking up and top end breaking up. 4-160 main, needle in middle same simptoms as step 3
5-155 main Top excellent, mid excellent, and low great slugish take off. then i checked the plug and dont even want to talk about it, but melted the end off
Crank seals are brand new dont leak* The bike ran good as i went lower aka leaner WHY!!!! Step 5 road around once didnt take long!!!!! Could be out of time?* im begging you people ive tuned alot of 4 stokes ive never seen anything like it???  

UR jetting why to high run a 150 to a 158 jet needle in the 3rd ring and ur air screw at 2 1/2 turns out run it for a shot while and check the plug also run your fuel ratio at 32 to 1  

you fix your problem by just putting the 38mm back on it.
you went from 66mm -76mm
that's a big jump, and the 38mm may be able to straighten that out.

have you tried going rich and trying to tune down.

basically if you are cutting out on mid range or top end then you are too lean.
if it is bogging down then it is too rich.
have you turned the fuel/air mixture with any of the new jets?