sr50 tuning problems

can anyone help my lad has changed various bits on aprilia sr50 (stage6 exhaust,teknix race clutch.5.5 rollers and 78 main jet and it now goes like apush bike and i don;t mean chris hoys more like old grannies. no accelaration and very low top speed

 

Stage 6 exhaust you need a 70cc kit and it sounds like it needs the carb fine tuning

 

If it was running perfectly ok before,put it all back to std!

 

i had a stage 6 exhaust on a 50 and ther fine good top end try a 75/72 jet
sounds like its not hitting the power band try lighter rollers or stiffer clutch springs