can anybody let me know how to time a b75 149cc. had to remove the head and droped the lolly now cant get to fire up ,have spark and fuel but no go.I have got top pot on comprestion and rockers rocking on bottom of both lobes so valves are shut.the dot on the cam pully is in line with the f line on the flywheel and it looks like the points are open but no go. am i missing somthing or do i just get to it with a hammer. help