Motorcycle Repair: Honda CB 400F SuperSport 1977, starter solenoid, honda cb

Question
I have a problem with a Fuse, that burns out from time to time, the 15A Fuse. Why does that happen and what do the Fuses 15A and SP15A connect? thx

Answer
Intermittent electrical failures are very hard to diagnose. Those two fuses are the main fuses for the electrical system.  Things like lights, horn, starter solenoid etc. are probably on those circuits.  I don't have a wiring diagram for that bike so I can't say for sure.  There's probably a wire that is coming in contact with a ground or some component that has a intermittent high current draw.  It's also possible that the fuses just get brittle and break due to thermal fatigue.  If you've added extra lights or other electrical devices those could be pushing the current draw up.

Regards
Rich