Stay away from them. If the failing fuse is not visibly burnt it is often just fractured as a result of age. Crimp connectors are a NO-NO on motorcycles. Vibration and weathering will eventually make them fail. Solder all wire joints you make and use a piece of shrink-wrap tubing to finish the job.
Solid wires are a NO-NO on motorcycles.
Vibration tends to fracture them. Always use stranded wire. These can be damaged if you use a test light on them. It is used to keep contacts within the connectors clean and to protect them from corrosion. Connectors in a motorcycle's charging system will melt and fail easily if those contacts are not perfectly maintained because the slightest increase in resistance will cause a huge amount of heat based on their large current loads.