I've recently bought an SW20 and the timing belt is running off the front of the cam pulleys by nearly a millimetre! The only reason I can come up with is that the water pump pulley isn't pressed far enough onto the pump shaft, since this seems to be the only thing which stops the belt falling off the front! (The guide washer on the front of the crank pulley isn't touching the belt at all..)
Has anyone else had this problem? Am I missing something?