Total Motorcycle Community Forums

All right, this is for a bike I don't own... yet.
I'm going to be looking at a 1976 CB 750. The owner tells me the main fuse blows at 4000 rpm, which he believes is related to the new accel coils he installed. He thinks it needs a new rectifier and/or regulator, and that perhaps they are overwhelmed somehow by the new coils. He also tells me the headlight has problems coming on, which strikes me as a possible symptom of a short.
I've got a 1974 360, so I'm somewhat familiar with the principles involved, but I don't know from 750's, and I know just enough about electrical systems to be dangerous.
If I buy this bike, am I letting myself in for an electrical nightmare? Anyone faced similar problems? Advice?
For the record, I've been known to ignore good advice before where motorcycles are involved.
Thanks for your help.

I have seen this before on CB750 and it always pointed or turned out to be the Rectifier.

What is happening is the alternator creates more guise at higher RPMs so the rectifier is so post to equal this out and it's not.

It will blow fuses instead of all your light.

It could also be a short in the harness so make sure you do the run down before jumping of the rectifier.

Good Luck!

Mike

Thanks much, Mike.
I bought the bike, found a regulator and a rectifier at the local pick n' pull junkyard, replaced the regulator and it still didn't work. Turned out there was some suspicious wiring that seemed to be causing it with the aftermarket coils. The previous owner and I worked on it prior to purchase and he figured it out.
I have had rectifiers go bad (my other bike doesn't have a seperate regulator that I know of) but they've always manifested themselves as a charging problem, not fuse-blowing. I think you can actually run the bike without a rectifier, it just won't charge.
Now I just have to chase down why the headlight won't come on and it's pretty much good to go.
And I think, with 2 bikes, I now officially have more motorcycles than sense.
-Chris