Making a single turn on a motorcycle is complicated enough; linking two or more corners in succession is even more challenging because you have to manage not only the corners but the transitions between the corners, too. It's a real feat of coordination to get these transitions just right. Quick-steering transitions, like what you encounter in switchbacks, chicanes, and esses are a necessary skill because, as your speed increases, turning quickly isn't optional—you'll run wide if you don't. When done right, quick transitions can be fun quite fun. Going from full lean one direction to full lean in the other direction other in linked corners is a genuine rush.
In switchbacks or other linked turns, properly timing the throttle and steering inputs is crucial. Accelerating out of the first turn, dipping the gas, "flicking" it over to the other side, then getting back on gas is the common sequence. The faster you go, the more fluid and precise that control sequence must be. As speed increases, a proportionately greater amount of bar pressure is required to flick the bike into the corner, making the required handlebar input almost abrupt.
Learning how to correctly move around on the bike is essential. Many riders tend to use the handlebars to pull themselves from one side of the bike to the other, creating conflicting forces—one force applied in a forward motion to steer the bike and another force applied in a twisting motion to move the rider across the bike. The rider may also be supporting his or her upper body with the arms, additionally restraining the bars. With the bars multitasking to steer, move the rider across the seat, maintain side-to-side balance, and support the torso, accurate throttle control and precise steering inputs are all but impossible to manage.
What happens then? The rider becomes frustrated by his or her clumsy riding or worse: "headshake" or other manifestations of bike instability appear. Headshake describes a sharp back-and-forth motion of the bars. The most violent form of headshake, when the fork rotates from steering stop to steering stop, is sometimes called a "tank-slapper" because it looks like your hands are slapping the fuel tank. Headshake is especially a risk in quick turning transitions where the front wheel becomes light as the bike rolls up and over its side-to-side arc. This becomes worse when acceleration is added to the picture; the wheel can even leave the ground. You can't steer effectively with the front wheel off the ground, and if the front tire comes back to the ground at an off-angle, headshake will result.
Experiencing any degree of headshake or wobble in transitions, most riders become hesitant to speed up, thinking it's probably only going to make things worse. Slowing down can seem to be the only remedy. It's logical—but not necessarily accurate—to believe you've hit some limit in either your riding skill or the bike's capabilities. Bumping up against the bike's limits is possible. More likely, though, the rider is creating the disharmony with conflicting bar inputs. Under these conditions, bike stability and rider stability are always connected. When the rider uses the bars for stability it transfers directly to the bike and creates instability, regardless of speed.
Learning to be less invasive while maintaining your connection to the bike is the best and easiest way to increase stability through quick-turning transitions. Conflicting bar inputs create instability and prevent precise steering and smooth throttle activation. Anchoring your lower body by squeezing the tank with your knees to stabilize yourself is one technique that works to eliminate instability. This may not be the entire solution, but it will give you a starting point for lessening this often-vexing problem.