Topic: dead electrical??

[biketaviousmaximus]

I rode my bike home with no problems several days ago, jumped on ths morning and it's D>E>A>D.........No lights, no horn nothing. The battery is brand new and charged. The fuse on the left hand side behind the little quarter panel is fine? Any suggestions???

[seaweb11]

Kill switch still on?
Check battery cables, don't just look at them "tighten them again".

[biketaviousmaximus]

Battery cables are solid, and the horn and indicators should still  work with the kill switch off?? It seems the ignition (key) switch does nothing...

[750goes]

Possibly your ignition switch is toast

if you can check  - there should be a red wire going into it - disconnect that one and measure if there is any power at that end - if not - check back towards the battery...

if there is power - check in the headlight bucket for a disconnected black wire coming from the ignition switch ??

happy searching

[bryanj]

Standard question WHAT BIKE!

[biketaviousmaximus]

Standard question WHAT BIKE!

Whoops, k2 750/4. 

It has 13 v at the red wire on the switch, but only when it's off or in the ignition spot i.e position 1 or 3....When I turn it to position 2 which is the usuall starting point, it reads nothing? 

I will try  a get it to an electrician, but I have the big ride of 2006 on the 9th december and I'm worried i wont be able to have the auto elec fix it by then. So in the mean time you guys might help me solve it?

[750goes]

can be a loose ignition barrell or its innards, but try another switch, sounds like it could be the problem - not definite though..

[biketaviousmaximus]

How could I 'hot wire' or short circut the ignition barrel?? It has 1 red 1 black 1 brown/white and 1 brown wire,,,,

[Jonesy]

Connect the Brown wire to the Brown/White wire (this completes the lighting circuit)
Connect the Red wire (hot from the battery) to the Black wire (main power buss).

Just so you can turn the electrics off between rides, I'd put a switch capable of 15 Amps DC between the Red and Black wires.

[bryanj]

Depending on wether you have the round (unique to 750) or square (same as 500/550) connector block will make for different ease of getting. Otherwise as said red to black-via some sort of switch and brown to brown white-dont need switch

[Bodi]

Try putting a tail light bulb across the battery, any old bit of wire from the "-" to the outer metal shell of the bulb end and touch the metal blob(s) on the end of the bulb to battery "+".
I've had a few batteries go strangely; the electrolyte tested fine, voltage on a meter was fine, but they would not supply ANY current. Some internal connection failed and killed the batteries.
Once you rule out a battery problem, check the ground cable (big wire from the "-" to the frame) at both ends. Clean the fuse block terminals and the fuse ends (MAIN fuse). Check the wiring inside the fuse block: disconnect battery "-" and remove the fuseblock, the back cover snaps off. All wiring and soldered connections have to be secure.
The main (key) switch is prone to trouble too but it sounds like you're losing power before there if there's no voltage on the red wire with the switch ON. That red wire should come directly from the MAIN fuse.

[OldSchool_IsCool]

I've twice experienced a main fuse that LOOKED good, but was in fact blown.  Swap it out or test with an ohm meter just to rule that out.

[biketaviousmaximus]

I tried to connect the red and black wires, but there was no horn et, do the brown wires need to be connectted to activate the nuetral dash light?

[OldSchool_IsCool]

Here is a wiring diagram that should be pretty close for your bike.

http://oldmanhonda.com/MC/wiring750K1.html

Basically, RED = unswitched power, BLACK = switched power and GREEN = ground

[oldbiker]

quote: It has 13 v at the red wire on the switch, but only when it's off or in the ignition spot i.e position 1 or 3....When I turn it to position 2 which is the usuall starting point, it reads nothing?

Connect your voltmeter directly across the battery. Now try the ignition switch. If the voltage drops to zero when you switch on, the battery has a bad internal connection and is toast.

If the voltage stays good, repeat with the meter connected to the red wire at the ignition switch.
If the voltage drops to zero when you switch on, then there is a bad connection between the battery and the ignition switch. (could be around the fuse area)

If the voltage still stays good, check for 12v on the black wire when you switch on. If you get 12v there then the switch is good. If not, then the switch is bad.

Try that and come back to us.

[biketaviousmaximus]

I connected the red and black wires and the brown/brown-white and got nothing, no horn et ......  Could the rectifier cause that?

[oldbiker]

No, the rectifier is only concerned with the charging of the battery from the alternator.
Have you tried an alternative battery yet? You MUST approach this in a logical order. Can you borrow a known good battery? Even a car battery can be connected using a pair of 'jump' leads to see if your horn and lights work.
Another easy way to check your battery is= Take it off the bike, give a full charge and then connect a spare headlight bulb straight across the battery. It should give a strong light for about an hour before it goes dim.

[biketaviousmaximus]

Hmm, it's a new battery and reads 14 volts on a volt meter, i think I'll get it to an auto elec, I kinda hoped that there was a likely problem but I guess an expert will find it (quick I hope).....

[teamleader77]

I would definitely try putting a new fuse in the main fuse position.  Older 750's are notorious for melting the fuses on the ends.  Mine just did this three days ago in the middle of a ride.  They look fine but do not work. 

[biketaviousmaximus]

Hey Guys,

Just letting you know the problem was the fuse block needed replacing (not sure what that means as yet).

I haven't picked the bike up yet but the auto elecs also fixed a faulty oil sensor switch and rebirthed my starter motor which I had been doing with out....... Sometimes it's good peice of mind to recruit the proffesionals.

[spacemonkey]

I just bought a 1976 CB750F and I've got the same problem.  This one has been in storage for about 20 years.  The tank is full of rust, so I haven't tried to start it, but I bought a new battery and wanted to check if the electrical was OK.  I added the acid, charged, and connected the battery.  Then I turned the key and...  nothing.   So tonight I replaced all the fuses in the little block behind the left quarter panel, reconnected the battery, and...  Nothing.  No lights, horn, ignition...  Nothing. 

I assume I need to try the steps above.  (I probably have to take the fairing it came with off...)  Any other things to look for?  Any advice for a guy who got a bike that has been sitting for 20 years or so? 

[spacemonkey]

Oh, by the way, how do I get to the ignition wiring? 

Thanks!

[spacemonkey]

I think I fixed that part of it.  I put the key in and turned the key back and forth for a while.  Eventually the indicator lights came on and the horn works.  I am guessing that the ignition contacts were just very corroded and turning the key eventually got a good connection. 

Now it seems that the starter switch is broken.  I'll start a new post about that.