I bought my 91 crx si with a just replaced, used from japan, i'm sure, sohc zc motor at 105k miles. I just thought about it, and that's low mileage to replace a motor. I did'nt ask the guy i bought it from, why he just changed the motor. I'm guessing, the original owner must have raped it(ragged it out). Edit: Just thought about it. He may have let the timing belt break. Weird, how you can answer your own questions after you post.