Figure 1 - Various types of bicycle goosenecks
Different style goosenecks are available to fit the type of cycle and handlebars used. Figure 1 shows various common gooseneck styles; a standard mountain bike gooseneck made of steel (left), a pillow block style BMX gooseneck (center), and a threadless aluminum goseneck (right). The first two goosenecks are designed to fit into the fork stem (steerer tube) and secure themselves tight by forcing a wedge against the inside wall of the fork stem. The gooseneck shown on the right of Figure 1 is designed to clamp directly to the top of an unthreaded fork stem. The wedge type goosenecks (also known as quill goosenecks) are the most common types you will be working with when hacking up bicycles, as they are widely used on lower end cycles. Steel goosenecks are easy to cut and weld when making your own custom steering parts for a cycle project.
Figure 2 - The wedge secures the gooseneck
Figure 2 shows how the wedge slides along the gooseneck stem, creating a friction fit along the inside wall of the fork stem it is inserted into. The top of Figure 2 shows the relaxed position of the wedge, allowing it to be inserted, along with the gooseneck into the fork stem and the lower image shows how the wedge is pulled up and out, creating a very tight fit between the fork stem and gooseneck.
Figure 3 - Steps to remove a wedge type gooseneck
If you have never removed a gooseneck from a fork stem, your first instinct may be to simply loosen the bolt and then attempt to pull the gooseneck from the fork stem, and this may actually work if the bicycle is brand new. However, the bolt could be taken completely from the gooseneck and not make any difference whatsoever. The "trick" to removing a wedge type gooseneck from a fork stem is to only loosen the bolt so it sticks up past the top of the gooseneck by about half an inch (left of Figure 3), and then pound it back down with a mallet as shown in the right of Figure 3. This action pushes the wedge away from the gooseneck stem, effectively removing all friction between the wedge and the inside of the fork stem. At this point, you will be able to hold the front wheel or forks, and then work the handlebars back and forth to pull up the gooseneck. Rust and dirt will be your only enemies once the wedge has been pushed down a bit.
Figure 4 - Loosening the handlebar clamp
To remove the handlebars from the gooseneck, the clamp must be relaxed by loosening the nut as shown in Figure 4. Usually, a few turns will be enough to loosen the clamp enough to push the handlebars free from the stem, but if there is a buildup of rust, you may need to remove the bolt completely to pry the clamp apart a bit using a flat head screwdriver. Be careful if prying an aluminum gooseneck clamp though, as aluminum is brittle and prone to break easily.
Figure 5 - Handlebars removed
The nut and bolt are shown completely removed from the clamp in Figure 5. Some goosenecks may have four bolts holding the clamp together. This type is known as a "pillow block gooseneck". A pillow block gooseneck is shown in the center of Figure 1. This style is often used on BMX bicycles.
Figure 6 - The long bolt and wedge removed
To completely remove the wedge, turn the top bolt counter clockwise until completely away from the wedge and it will come out as shown in Figure 6. As you can see, the angle of the wedge matches the angle at the base of the gooseneck stem so that it can slide up and down. Some wedges are actually round plugs that spread the end of the gooseneck tubing out, but essentially the operation is the same - a friction fit against the inside wall of the fork stem. Goosenecks come with many various stem lengths, so keep the proper bolt along with the gooseneck in your parts collection.
Figure 7 - There are two distinct sizes of stems