110cc pitbike

Got a Chinese pitbike 110cc and I can't seem to get it to run... it has spark compression and the timing is setright... I have cleaned outthe carb 3 times and hve tried tuning it about 6 (resting needle clip) i have tried a lot of things and this is what I have found out... itwont start at all...

ok so i bought a 110cc atomic pitbike the other day andi have been rdin i around great bike lots of power and fast! anyway say i will be goin in 3rd gear and it will all of a sudden change into 1st or 2nd when this happens it slows right down and it is very dangerous what could be the...