Quite often what you feel is at the front of the bike, comes from the rear. I've had crashing, lock to lock tank slappers on three occasions, and twice got flicked over the front by not letting go of the bars quickly enough. The hydraulic steering damper will usually stop it from happening unless the bike is really badly set up. If you immediately let go of the bars when it happens, and grab the tank to stay on the bike, you will find you have plenty of time to grab the bars again- but don't do it too quickly. It is very deceptive - what can appear to be a mild shaking of the steering head can launch you off the bike. Try to keep your sense of humour and don't react too quickly, if you fight it you are gone.