Have a read about steering axis and trail. Head shake (instability) is when trail gets close to or in front of where the steering axis intersects the ground. Some of the ways to move trail behind the steering axis are; - Lower the forks in the triple clamps - Lower the rear of the bike - Increase front tyre pressure Proper spring and sag setup for rider and bike should get the geometry right to start with. Stability can vary with terrain such as sand which moves the contact point with the ground much further forward causing negative trail. This is where a steering stabiliser comes in handy. I found a good book on the topic called "Race Tech's Motorcycle Suspension Bible" in the Kindle store online.