Topic: CB750a blowing main fuse

[tutnai]

Short story - Purchased non running '76 for $100 last year. cleaned carbs, replaced battery, changed fluids and running by last winter. wrapped pipes, dyna2000 and added ContiGo's this spring.
Minor propblem - Speed sensor not working since no speedo cable and idle adjust for getting into gear is delayed. Solve minor problem by starting on downhill.
New problem - about 3 weeks ago, battery charge was going away afeter sitting for a day or so. Then after about a nice 30 minute ride, all dies. Lights everything gone. Notice 15A main fuse is blown. Swap with spare, turn key, lights on, fuse blows. OK, open seat to see what is going on. Nothing obvious, swap in new fuse again. Fires right up. Let it warm again, point down hill  , close seat. Blown fuse!I continued this for a while of swapping fuses and trying various seat closings - gave up and got a tow. Now in the home garge, fuse blows without seat. Still cannot find a short cause. Any ideas where I may look?

[Bill/BentON Racing]

Blows when? Soon as you turn on,within 10-15 secs,? If not try using brakes,turn signals,horn,etc.see when it blows...try to isolate.Get a wiring harness diagram,but you can start with red wire from battery,end up @ main switch,key on red goes to blk switched hot,see what happens.Insulation worn off wire probably, and pull headlight check inside,wire loose touching ground? Good Luck,Bill

[tutnai]

Thanks Bill,
THis blows within 5 seconds. Last time blew the fuse in half nice pop.
I am following the + looking for stripps and grounds. Nothing yet.

Frank

[Danno]

if it was me i would bet that your dyna is pulling more power that the bike is used to but I had a 76 that had this problem and it was the voltage regulator which could have been screwed up by a short or bad ground

[tutnai]

It WAS the regulator - thanks