my 96 sporster has a hammering or knocking noise in the motor can not locate noise wether in top or bottom of motor. there is no loss of power does not smoke oil is clean and full. I tightned the chain in the gearbox it was a little lose but that did not fix the problem. does anybody have any ideas of what the problem could be. I would like to make itt to Sturgis yet this year. please help me out if you can