Motorcycle Repair: Aprilia rs 50. 2009, aprilia rs 50, oil injection system

Question
Hello William. I recently came to possess a Aprilia RS 50cc. Once i got the bike i noticed that it was very sluggish when pulling off, even though it starts first time every time. The bike has been tampered with. Previous owner had cut the air filter pipe off. (Which connected the carb too the air filter box) and stuck a K AND N filter in the carb. Thinking that this may be letting in too much air, we covered it up but still had the same sluggish problems. We tried to reset the mixture too. but it still has the same problem. Once warm it idles ok with no choke, but it does smoke allot (white smoke) my experience from 2strokes when i was young suggests this is a bit more than normal. What the bike actually does is...It pulls away sluggish, at 5000 revs starts sputtering bad. yet punch through to 8000/9000 revs, it takes off quite rapid. We don't know what has been modified apart from the filter. We have cleaned the carb too. each gear it the same, it just seems to be very very sluggish, then splutters. hit 8000/9000 and its a rocket. Any ideas to what our next move should be would be greatly appreciated as all bodywork is done. thanks

Answer
It sounds to me like the carb is jetted incorrectly and maybe in need of an
inspection. I rebuild carburetors for a living..  www.viragocarb.com
I think a complete tear down and inspection and new carb kit installed might solve your issues.
The white smoke is maybe to much oil in the fuel research the mixture. 3o/1 or 50/1.
If it is injected there may be a problem with the oil injection system. Try to acquire a service manual for it.