pulse lightspeed 2 125CC feels like I'm riding a 50 help please!

So I got this bike a couple of weeks ago it needed some work, which I got done,new rrollers (same weight as old ones) new belt, new rear brake pads and a new rear tyre, an MOT. so I'm riding around today, the bike is most definitely a 125, but it's so slow it feels like I'm riding a 50. Any ideas why? It passed MOT not a thing wrong with it just feels so so slow!!

Rubber parts ages & crached http://7car.tw/articles/read/15261 /Dirty air filter / Valve clearance NOT ok (According to Kymco GY6D shop manual in/ex 0.12mm )
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Enricher ALWAYS on
http://www.motorfans.com.cn/bbs/view...originator=yes
Hidden ??? in exhaust
http://www.motorfans.com.cn/bbs/view...originator=yes