[jonnywombat]

There is a lot of science going on to understand and prevent tank slappers, with the goal to design them out of bikes..

Put simply if you are going just the right speed and hit just the right series of bumps it will cause an oscillation in the bars. Instead of dying away, like a normal twitch, they increase in severity.. as the frequency of the oscillation matches the harmonic frequency of the bikes steering/suspension set up..(the same phenomenon that makes a tuning fork hum, or the Tacoma narrows bridge collapse) causing positive feedback, so every wobble feeds the next larger one.

If you experience this then apart from prayer you can take steps to try to reduce it..(although no guarantees here).. the way to try and regain control is a little counter intuitive... you have to release pressure on the bars, allowing them to move freely, and gently roll out the throttle a little bit..(but do not shut off completely)

Do not grip the bars tightly or apply the front brake!!!