24/7problems

hi im having similar problems,i have a dt125r 2003,just had new piston etc,somtimes really smokey wen start it,sometimes spluttering at high revs 6/7k and the sometimes bogging in high gears but low revs,powervalve is in fully working order so is the air filter etc,could this be a problem with water in my carb as the weather hasnt been the best recently? or is it the crank seal,how do i check the oil filter? and my bike does clear out the smoke after just taking it down the road,thanks please help