2006 tsunami 125cc wont idle

[amatuer]

The day i got the bike, after about 6 hours of solid riding(would idle perfectly) i was on my way back home and the chain got caught and destryoed the casing and magneto. i sent it in to be fixed, once i got back i still needed more parts before i could use it, and i put it off for a while, now that i got it all fixed and just started riding it i noticed it wont idle, and that when im in 4th gear it does not got as fast as it use to, it just sounds like its reving if i go past half throttle on 4th gear. im hoping its just a small problem, and if anyone has any suggestions on how to fix it please let me know, ive already spent a lot of money on the bike and would rather try and fix it myself.

thanks