well, how small is the pinhole?
and are you using film or paper?
last pinhole I used was a paintcan pinhole with ilford paper. took about two minutes to make a somewhat underexposed picture.
try halving the time you expose the film or paper or whatever by and see what that does. if its overexposed, half the half. if it is underexposed, expose halfway between the time you were previously using and the half of that time.
just kinda try to dial in your times and you will get it.