If he's anything like my dog, he saw a bug fly into the closet and now he KNOWS there's a bug in there and he WANTS to chase it. My girl Cooper's weird-obsessive about things like that sometimes.
Hard to imagine something in the bloodwork that's going to cause a fixation on a closet. But what do I know, I'm not a vet.
Also, it could just be that he never saw bikes as a pup, and never socialized to them. Cooper was rescued from a box by the side of the road, and so knows all about most sorts of vehicles, and has basically no interest in them. But several things she saw for the first time after she was a year old freak her out, including people of certain ethnicities. That's right, my dog's a racist.
