Looking for classic motorcycle parts can be difficult, especially if you don't know what you are looking for. It helps to learn as much as possible about your classic motorcycle so you have a better understanding of the parts included on the original model. By knowing the original parts and their function, you will be more likely to find classic motorcycle parts to replace them, or modern parts that will work just as well. The best parts will also depend on why you are replacing the parts in the first place. Aesthetic enhancements, for example, may require a different part than a functional upgrade.
Decide whether you are looking for original classic motorcycle parts, or if reproductions will be sufficient. Original parts will very often be much harder to come by, and you may need to visit junkyards, antiques dealers, vintage motorcycle dealers, or online resources to purchase vintage parts. Be sure to research as much as possible about the parts, as many dealers will try to pass off reproductions as originals. The more you know about the part, the more likely you are to be able to recognize a reproduction. Be sure the part you buy is in good enough condition that it can be used on your motorcycle for a long period of time.
Sometimes it is acceptable to use reproduction parts instead of classic motorcycle parts. This is most common when classic motorcycle parts cannot be found or no longer exist, or if the classic parts were not high-quality enough to begin with. Newer parts may be a worthwhile upgrade both in terms of aesthetics and function. When choosing parts that are reproductions, be sure to choose parts that will fit your classic motorcycle properly, or can be manipulated to do so. This may take a bit of research so you can find the most appropriate parts. It is also a good idea to visit a motorcycle shop to get recommendations for the best parts.
One way to track down the best classic motorcycle parts is to contact the original manufacturer, if it still exists. While it is unlikely that the manufacturer will still make parts for your classic motorcycle, the employees at the manufacturer may be able to recommend the best places, in person or online, to get ahold of classic motorcycle parts for your bike. Another good source for information is vintage motorcycle clubs, which can usually be found online.