I worked it out! I have been test running the engine without the air filter. That hasn't caused me problems in the past with other engines when testing them but this one was different. I also don't have the proper cover for the air filter ( recycled mower with bits missing) and the one I have has a hole in it for the primer bulb but the mower has an auto choke and its proper cover doesn't have that. Anyway, when I covered the air intake with the filter the mower ran fine. I hope this helps others from wasting their time.
