Some companies sell their engines with a 30 day or at least a startup warrenty. Aside from the obvious like a hole in the block, there ins't any way to really check if a removed engine will run without tearing it down. I would definately ask whoever you buy an engine from what kind of warrenty they offer to protect yourself and get it in writing as well. If a company refuses to offer a warrenty, or something sounds fishy, look elsewhere. There are lots of B18C1's out there so shop around till you find a place you feel comfortable buying from.