XS750-blowing the main fuse

[meaganheinxs]

Hi Folks,
Im rebuilding a 1977 XS750, a few weeks back it was incredibly close to starting, I thought maybe the battery I was using wasn't strong enough so I used hooked it up to a car battery.... since that little escapade every time I turn the key the main fuse blows. I have searched top to bottom and cannot find a short. Additionally, this only started happening after using the different battery. This leads me to believe that its the voltage regulator causing the issue. As the bike doesn't run I cannot test the regulator as described in the manual. Does anyone know if the regulator can be tested even if the bike doesn't run? Perhaps its not the regulator at all? I'm stumped

 

[Jan_P]

I have no knowledge of that wiring
But on a xs650 the power goes from ( not running )
battery to ignition , and to starter engine
And then further downstream in the wiring
to other fuses that are smaller. ( Not always existing on early models )
So if the main fuse blows the fault is in that part described above
( battery to ignition , and starter engine )
pre subsystem fuses
Otherwise the smaller downstream fuse will blow
In your case assumption the charging circuit.
If this does not help please come back preferably with a link to the wiring for exact model bike.
On XS 650 the first place to look is the rubber grommet going in to headlamp
If not there I would most likely disconnect the wires going to starter
But again please come back with the wiring.

 

[meaganheinxs]

I attached a picture of the wiring diagram i hope it’s clear enough. I’ve checked the headlight bucket a

nd it looks good. I’ll take a look at the starter, appreciate it!

 

[Jim]

You can see if the regulator is blowing the fuse just by disconnecting it. With it disconnected the regulator and rotor (downstream) are removed from the system.

Additionally, this only started happening after using the different battery.

Might be a silly question, but are you certain the polarity's the same as the old battery? Considerin' that's when the problem started, might be worth double checking.

 

[Jan_P]

Hi
I shall look at the schematic
one way forward can be to remove all other fuses except Main
is there 4 ?
And switch on

 

[member28833]

So the fuse blows immediately just from the switch being turned to the on position, before even pushing the starter button?
Maybe its the switch itself.

 

[Jan_P]

You can see if the regulator is blowing the fuse just by disconnecting it. With it disconnected the regulator and rotor (downstream) are removed from the system.

Might be a silly question, but are you certain the polarity's the same as the old battery? Considerin' that's when the problem started, might be worth double checking.

Yes by looking at the schematic it looks as if the power on ..goes to the Main Switch and then to the regulator Br
Brown
before reaching more fuses

So disconnecting the regulator is a smart test .. 3 pin connector