Topic: mysterious blown fuse

[turkey4me]

I have a 76 750F that has been running great until today.  I lost my head lamp power and tracked it down to a broken wire at the 8 prong plug.  After reconnecting the power I got the bike and the head lamp running.  Went for a ride and made it 10 blocks when the bottom fuse blew.  Walked home, replaced the fuse and the bike would start and run until I kicked it into gear and put a load on the motor.  I removed the head light and checked all the wires for a short.  Could not find anything obvious.  I managed to start the bike and with the head lamp removed, rode home.  Seemed to run fine until I put the head lamp back together.  Blown fuse.  I removed the head lamp again and now the fuse blows immediately after I turn the key.  I noticed the green/red wire for the neutral lamp (which I have by passed by directly connecting to black power) is warm and so is the small black diode after the fuse blows.  What gives? 

Can someone help me trouble shoot this issue?

[madmtnmotors]

Corroded terminals/connectors often eventually add up to over-amping circuits. Takes me about two weeks to do the entire harness and switches. Usually just doing the main connectors help a lot:


http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191

[turkey4me]

Im so cornfused!  I just put in a new fuse.  It did not blow this time but the bike wont start. There is a small black diode that hangs loose by the starter.  It suddenly became very hot. I turned off the key.  Waited ten minutes and it has cooled off.  Now with the key on it remains cool and does not get hot.  there is a small fuse in the diode.  When I remove it I have power across diode.  I also have continuity across the diode fuse I removed 18 ohms.  Still no power.  Can someone tell me where to go next?  Neutral switch or clutch switch?

[madmtnmotors]

I noticed the green/red wire for the neutral lamp (which I have by passed by directly connecting to black power) is warm and so is the small black diode after the fuse blows.  What gives? 

Can someone help me trouble shoot these issues?

FTFY

You are describing two different items that may not necessarily be related. Electrical issues are usually best resolved systematically, one at a time. With that said, let's talk about the first item:

I noticed the green/red wire for the neutral lamp (which I have by passed by directly connecting to black power) is warm

Which red/green wire did you connect to black? The red/green wire to the bulb, or the red/green wire that continues down to the neutral switch? Here's what you can expect as a result of your "experiment" of connecting red/green to black:

>If you connected the red/green lead from the neutral bulb to black then I would expect no issue... and no neutral light either, regardless of gear selection (including neutral).

>If you connected the red/green lead from the neutral switch to black then as soon as you shift into neutral you will have created a dead short since when in neutral the neutral switch completes the ground to light up the neutral light...

[turkey4me]

The lt green/red neutral switch at mid ship is connected to ground at bottom of motor.
In the head light bucket there is a lt green/red lead that is not connected to anything as I'm not running a neutral light.

There is also a dark green/red lead that is connected via two separate leads to black.

I checked voltage on every lead coming from either the bike or the controls into the head light. 
The only leads with no power are the brown/white lead from the bike for gauge lights are dead.  I also have no power to the white head light lead from the left control.  I have tail and signal and brake lights.
Tomorrow I'll open up the left hand control and see what I get there.

[PeWe]

Im so cornfused!  I just put in a new fuse.  It did not blow this time but the bike wont start. There is a small black diode that hangs loose by the starter.  It suddenly became very hot. I turned off the key.  Waited ten minutes and it has cooled off.  Now with the key on it remains cool and does not get hot.  there is a small fuse in the diode.  When I remove it I have power across diode.  I also have continuity across the diode fuse I removed 18 ohms.  Still no power.  Can someone tell me where to go next?  Neutral switch or clutch switch?

[PeWe]

Check both handle bar witches with wires. Short to ground (bar), squeezed wires and bad solderings in the crappy connectors.

[trueblue]

Fit a festoon bulb in where you would normally put the fuse, the bulb will light when the short is active.  BTW, you need everything switched off except the ignition.  Otherwise it will light up simply because of circuit load.

[turkey4me]

Still sorting through the issue with everyone's help.  I did find at the Key switch there are 4 wires; Red, Black, Brown and Brown/White.  In run position I am getting voltage at red, black but nothing at the Brown/White wire.  Does this suggest a short in the key switch itself? 

[calj737]

Brown and Br/White are auxiliary key position. Check to see if you get 12v with key moved into Aux.