Section K3 in the Workshop Manual (which really is the owners manual these days ?) under Routine Maintenance says valve clearances every 3000 miles.
But if its just been rebuilt - before you go out the workshop door, again at about 2 miles after the once around the block, after the first head retorque, and then with each head retorque. And if you hear any funny noises....
Opethiselps.