choice in pipe doesnt really matter. idk where you got that idea.
trying a bigger carb may be ok seeing as you have a port job. have any head work? depending on port specs, you may want a different pipe.....
factory carb is a 26mm mikuni. you could try a 28mm or 29mm and be ok. i would wait to go any bigger unitll you add a BB or stroker crank. then you could probly bump it to a 34 or so.