What RCKen said:
The engine will fire and run backwards if it's flooded.
Some engines do this more than others due to the engine timing. You should never just prime or choke an engine and then start flipping or bumping with the starter. This is the best way to throw off the spinner and prop when it kicks back.
For a two stroke glow:
Instead, after it is "primed", hook up the glow plug and pull the engine through compression by hand. If it kicks, it is flooded, keep pulling it through compression until it doesn't. Quite often it will start bumping every other turn through compression. If flipping with a chicken stick, flip right after the bump, or with a starter.