Comet 125 cutting out

Hi there I have an 05 comet 125 bought secondhand last March ran fine until August when I decided to respray the tank.I put the tank back on the bike started up first time but cuts out as soon as I engage 1st gear.I have recently replaced the entire wiring loom as previous owner had chopped it to bits, I thought it may have been a faulty wiring on the kick stans switch but still cuts out in first. Could it be the clutch? I need help if anyone can offer me any.

Thanks in advance
John.