for RS125 new riders, please check that your engine oil is not milky tru the glass often. if it so, be prepared to change your balancing gear. $250+
i suggest not to mod your bike if you're gonna ride it daily. like open ports; block skimming; bigger carbs, bore kits etc. (unless you owned a petrol station)
IF you insist on mod, just change tyres to a thinner ratio, CDI. and carb jetting will do.
lastly, dont waste your cash/time to mod small cc bike, wanna go fast, buy 1000cc. safe riding.