Topic: 1975 CB750 Electrical Help --PLEASE!!

[Fenix500]

Guys - Not sure what I did. Something stupid I'm sure, but could really use some help on this.

I have a 1975 CB750 running beautiful all week. Then...yesterday I used it to jump a buddy's bike that died on our ride. My bike was off but I had the ignition switch on. He cranked over his bike and mine went dead.

Now I have NOTHING electrical working. Went through all the obvious stuff - fuses, battery, grounds -- to no avail. Can ANYONE give me some feedback or ideas. I've connected the battery leads to my car battery to see if I get anything and NOTHING happens. I'm at a loss.

Gotta get back on the road.

Thanks,
FENIX

[JohnG]

get a test light or multimeter  (in DC volts mode) and start at the + post of your battery and keep following the voltage until you lose it. Fuse box next. Check both sides of your main for voltage.  Just because the fuse is OK is not enough.  Many of us have seen those boxes melt.  Watch for corroded connections that got overwhelmed by the extra current draw of the second bike.

Do you have the wiring diagram

[the technological J]

my fuse box shorted just under the box in the wiring it looked completly normal until i looked closer... look for anything that looks hot or melted.... jump ur selinoid posts just to rule it out...(pull the rubber insulation covers and use a screw driver to jump the posts) make sure shes in nutral

[Fenix500]

Ok guys. Got home from work and tried everything you suggested. The test light comes on when the main fuse brackets are touched (Neg and Pos). Interesting thing is it DOESN'T come on if there's a fuse in the box. Also, did the solenoid neg and pos and the test light lights up. Any other ideas?

Fenix

[JohnG]

Is the key On or Off when you are testing?

When you say you touched both sides of the main fuse and got light, was the fuse in place or not??

[Fenix500]

When key is on and NO fuse. Light is dim. When key is on NO fuse light is bright. When key is on and fuse is in nothing. I tested all the way through the ignition switch and test light comes on.

**Also checked solenoid and it's good also. The main fuse itself get fairly warm when the key is on as well.

[Fenix500]

Is it possible a fried voltage regulator or diode can do this?

[JohnG]

What is your main fuse rated at??

Do you have access to an Ammeter??  Voltmeter??

Do you want a wiring diagram??   I can scan one in tomorrow.

[Fenix500]

I have a wiring diagram and have been pouring over it. My feeling is it has something to do with the fuse as well. Can a fuse with the wrong rating be a problem?

I really appreciate your help on this. I'm pulling my hair out.

[JohnG]

If you have a short of some kind which is drawing alot of current, then the fuse should blow  (if its the correct rating).  If someone puot the wrong fuse in  (too high a rating) then it would not blow but all the power would go to the short  (path of least resistance...that kind of thing).

I believe 15 A  is the correct Main fuse. 

The reason I mentioned an Ammeter is you could remove the Main fuse and put the Ammeter across the two places on the fuse box and see what kind of current is there.  They are not expensive and from time to time worth having around.

[the technological J]

this was my thread and im just showing it to u for the pictures sake... the short could be hiding and looking completley normal

http://forums.sohc4.net/index.php?topic=53293.msg570734#msg570734

[Fenix500]

thegabrielj -

You were right on the money. After several hours testing, unplugging, cleaning and cussing. I found the culprit. Behind the fuse box and the main circuit the connection had eroded sufficiently to give a ghost of power but not enough to carry a current. I am currently rewiring the fuse box with a 4 circuit ATC box. ON a positive note I did a very nice cleaning of connections and wiring map!

Thanks for ALL the input and feedback JohnG  - everyone's suggestions made the job a lot less painful!

Fenix

[JohnG]

Glad you got it!!!  All the cleaning will pay off in the long run too.

I feel bad I did not mention checking the fuse box for becoming junk as I know they do that from time to time, for no apparent reason.

[motocyconomad]

I am in this kind of a fight too goddamit I have to find my zen when it comes to electrical