I've just bought a Honda CB250n 1982 and whilst

SOURCE: Hi I've just got a Honda cb250n and there now

Hi if you havent already checked the fuse at the starter solenoide 30amp check it first. Next locate the rectifier this will have 3yellow wires these come from the alternator and provide AC voltage to the rectifier which is then converted to DC voltage used for charging the battery, at the rectifier you have green wire/s this is the earth and red wire/s this is the voltage in and out, it is here at the connecting block you must inspect the condition of the wires do not unplug the block simply check for oxidiseing which is visible to the eye and is green in colour, simply twist and pull gently on each of the wires to check for conectivity, if any break off you can bypass the block by removing the wire from each end .next it is not uncommon on the old 250n for the ignition switch to become faulty, using a test light if you dont have one make one up by removing one of your indicators, the coloured wire orange or blue depending on which side you remove is the indicator live wire, at the ignition switch using your test lamp check for 12 volts by placing the coloured wire on the red ignition wire your lamp should light if you have voltage here, if you dont have power trace the wire back and look for breakages in the wire, you could also run a new wire from the battery to the switch and with this connected the switch should opperate normaly