Hey i got a 2000 kodia 400. 401 cc belt drivin wont rev up properly when im driving it/revers. revs up fine in park/nutreal. Seems to back fire alot.does this sound like i need a new belt. N cleam up my carb? Maybe adjust my throttle cable a bit? I can only get around 30 to 35 km/h outta this machine i figured i should je able to get around 60 or 65 outta it . Slack as heck