Originally Posted by
79pmooney
To follow DiabloScott's thought, maybe ride the bike, do that hard start and feel the clunk, glide to a stop, put the bike in a solid strand (or tie the front wheel to a tree) and try pulling the rear wheel back and see if you can get that second clunk. Look for any cracks between teh BB shell and the rear dropout, especially on the right chainstay. Special attention the the chainstay to BB joint and chainstay to dropout joint. If nothing there, I'd then look along the seatstays.
Ben
If the chainstay is cracked, it ought to show itself with a little force applied from the side - just hold the bike up with the brakes on and sort of step on the chainstay or BB laterally and vertically (like we used to do for evaluating how flexy a frame was) and listen for crunchy noises. OP's bike is aluminum so it should be obvious.
And yeah, near the dropout and the BB are the most suspect places, unless there's damage from a kickstand or something.