Topic: Blown fuse. Where to start?

[mazingerzeca]

Hello all.
The bike is a CB750 K8. This morning I didn't shift into gear well and accelerated in neutral. Then the main fuse blowned and everytime I changed it the new one blowned again. I disconnected the headlight fuse and with this fuse disconnected the main fuse didn't blown. When arrived home, I checked the headlight and it was blown too. I thought that the headlight had blown first, and as a result, without that light, the electrical installation was overcharged and it made the main fuse blown. So, I changed the headlight, put new fuses on every place, but after a short ride, the main fuse blowed again. This time, putting the headlight and taillight fuses off didn't make the trick. Everytime I turn the key on, the main fuse blowns (15A). Even putting a 20A fuse it melts. I have the suspicion that the rectifier doesn't work and the installation gets overcharged, blowing the main fuse. Sorry for my electricity ignorance, but now it seems as if everything was "overcharged". What should I do? I have a spare rectifier. Do I try this? Can I do anything to "discharge" it (if it is truly "overcharged") before changing the rectifier?
Thank you,
Ignacio.

[tlbranth]

It sounds to me like your voltage regulator isn't working right but I haven't messed with those since the 60's. There are regulars on this forum who know the charging system quite well and will undoubtedly chime in and fix you right up. Good luck

[mazingerzeca]

I checked the battery output and it's around 12, so it doesn't seem to be overcharged. Right now, just putting the key on the fuse blowns, so it seems to be a shortcut. How do I find it?

[tlbranth]

The battery's always going to be 12-ish volts no matter how many volts you throw at it. When the engine is running, though, does it measure more than that ...... a lot more than that?

[BVCB650]

Should be no more than 14-15 when running at say 4 grand.

[mazingerzeca]

Thanks for the replies. Found the shortcut. It was one of the yellow wires from the alternator to rectifier. It was touching ground and blowing the fuse.