I had borrowed somebodies motor one spring and I set it up in a garbage pail to check it out and make sure everything was fine. It started first pull, but after idling a bit I noticed that it wasn't peeing at all, so I said that maybe there was a thermostat, but a few minutes later (because some water was splashiung up from teh pail i heard some sizzling so I turned off teh motor. Got on teh phone and called my buddy who I had borrowed thmotor from to see if he knew why. He said when you start it make sure to give it gas and see what hapens diod that and it started peeing right away.
Try that maybe.