I've read about guys experiencing head shake and Tank slap and was wondering if someone can shed some light on what exactly it is, why it happens, how to react and how it can be prevented

 

Head shake is caused by the front tire becoming "crossed up" with the rear. The condition can also be caused by reduced weight on the front tire at which time a side input is introduced.

For example (in racing), I'm exiting a left turn and setting up for a transition over a hill and to the right. Since I'm on the gas and flicking the bike from left to right up a hill, I always see a shimmy as I crest the hill. The forces of countersteering plus the lightening of the front end equals some minor complaints from the chassis.

A tank slapper is just another term for head shake, however, a tank slapper is much more violent and usually tosses a rider off the machine. Some bikes are prone to head shake when ridden hard....it's a geometry thing.

Do not fight the bars. If you have room, hit the gas at a point when the bike is not leaned over. Doing so will take the load off the front at which point you can muscle the bike back into shape. Whatever you do, do not load the front end if you can help it. Loading the front end will typically increase your symptoms of head shake.

 

And get a good damper, it will save your ***. Even the HID on my 1krr works well as long as your hauling ***. Saved me at Jennings last year when I ran wide out of turn 1 and hit a divit at the track edge. The Ohlins, Scotts and grp are all quality after market dampers.