It is a model 138f693g118. It has a bad engine and I'm trying to put the new 18hp B&S on there but I've run into a snag taking the old one off. I cannot get the pulleys/sleeve off of the old engine's shaft and so I can't get the old engine off of the chassis. I don't want to damage the old pulleys because I don't think it would be easy to replace. It has been soaked with WD40 for the last week and still nothing. I tried a gear puller yesterday and nothing. The bottom shaft bolt is out and I didn't see anything else securing the pulley sleeve onto the shaft so what do I do now? All help appreciated!!