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!!