It should work either hot or cold, Andy. I usually do it cold simply because I like to do bench work on cold engines. I only start them when they are on the floor, and because I only have Hondas these days and they are very heavy, I try to move mowers between bench and floor as infrequently as possible. So, all the bench tests happen in sequence, then all the floor tests (which are performed with the engine running or having just run) happen afterward.
