electrical problem on cb750k8

im looking at purchasing a 75 cb750k8 from a friend of mine, he has had the bike for about 2 years and i know it always ran well for him. at the end of the riding season last year he said he was riding home and the headlight went out. now we pulled it out of the garage and it wont start. im not getting spark at the plug, or lights. for lack of the proper tools i spent a few hours testing the electronics with a light bulb just to make sure everything that should be getting voltage was getting voltage. I successfully had power at the lead that powers the coils, into the power switch in the handle bars, going into the voltage regulator, the instrument cluster, and 1 of 3 fuses. while tracing back wires i noticed everything that was being problematic all in directly or inderectly ran back to the voltage rectifier.

so my question is this...could it be the rectifier and/or regulator. would this be the behaviour i would expect if one of those were bad. and how would i go about testing those? i do have a multimeter for testing. i just didnt have it available last chance i had to work on it.

check the wiring diagram for that bike. The output of a regulator is connected to the battery which also will be connected to everything else that uses 12v. remember some items also run through a switch...even the headlights, even if it has no OFF switch. Lots of modern bikes' start buttons are wired to break the electical connection to some electronic devices that have no off switch, just do divert all the current to the starter and remove the excess load that items like headlights place on the battery when not needed to start. so if the wires are good and nothing is spliced, the fuses are good, check the connector pins. i've actually found some corrosion in the pins that were keeping connections from being good.

Get yourself a multimeter if you haven't bought one by this time. it's not only good for just checking voltages, but also a must to ohm out from point to point. just because you have your required voltage does not always mean that your end item will work. Everything added in a circuit adds resistance. even an ohm or two can cause you problems, that's why you need to have a multimeter.