Topic: tackling my electrical issues...

[babyfood1217]

Best place to start?  I'll describe my issues for you all, then perhaps you can point me in the right direction...

1976 CB750k

The only electrical modification is the removal of the blinkers, the little turn-indicator-buzzer, and a new taillight (running the same 1157 dual filament bulb)

I noticed that while trying to start it up for the first time since last fall that it...well...wouldn't.  I couldn't figure it out, but I finally looked at my main fuse, and noticed it was blown and there was a tidbit of corrosion near the other two fuses.  Now, the last time I had fuse issues was when I had my blinkers still attached (I didn't had time to search for the short, so I removed them), so I was a bit curious as to why is was blown.  Well,  none of the stores around me had 15A fuses, and the places that did were sold out, so, being the impatient little bastard that I am, I threw a short section of steel rod in the place of the main fuse ( I know this was dumb, but it's in the past now.)  Well, the bike fired up and worked fine.  That was a couple of days ago, and today, after welding together a license plate bracket, I said to myself "I would like to ride around the block", so I turned on my bike, saw both the neutral and oils lights go on, turned the petcock to "ON", opened the choke just a hair, and thumbed the starter.  Well, it turned over once and died.  And not just any death, it was a complete death, with lack of lights and everything.  I ckecked some random important bits and saw nothing out of the ordinary (charred electrical connections, smoke, other blown fuses, fire, etc...), but couldn't get anything else out of it.  I would like to tear down the electrical system in the next month (to find the short that was affecting my blinkers), but before I do, I would like to figure out this new problem.  Any ideas on where to start?

-Chris Gerber

[TwoTired]

I'll probably regret this...
But, do you have:
1 - A wiring diagram?
2 - any kind of electrical troubshooting device I.E. a Voltmeter, ohmmeter, DMM, continuity tester, or devining rod?
3 - battery charger? preferably automatic
4 - a new supply of patience?
5 - a 15 amp circuit breaker?
6 - The proper fuses?

Have you done a search on this forum for melted fuse box?

[babyfood1217]

Here's what I have got...

-The wiring diagram from a Clymers manual
-An Ohmmeter and a Voltmeter
-A battery charger with Automatic setting (its a 10A charger, as opposed to the desirable 2A or 3A models, but I've used it before with no problems)
-I will get the proper fuses on Monday
-More patience than you can imagine (as well as a college spring break starting on Friday, so I'll have time too!)

I don't have...
-A 15A circuit breaker.  Do they make these for automotive/motorcycle applications, or does one just jury-rig something available fo home use? 

Also, upon waking up this morning and letting the bike sit for approx. 14 hrs, I went to and switched it on, and low and behold, it lit up!  I was afraid to thumb the starter again in fear of killing like before, but it makes the situation that much more curious. 

-Chris Gerber

[crazypj]

Check the battery terminals are tightened up or remove cables and clean first, putting chardger on  and off bike may have loosened them. Check the main switch terminal block isnt loose. Indicator shorts are relativly common, the wire inside the arm gets damaged rather than main harness damage.
PJ

[number13]

Last time I had that problem, (push starter, kill bike),
it ended up being a loose ground connection where the
negative (black) battery cable bolts to the frame.
The fix was clean well and tighten securely.
best of luck, mate.

[TwoTired]

If you are regularly blowing fuses in a circuit that is intermittant, using a circuit breaker while fault finding is cheaper than fuse replacement.

Basically, you clip the breaker across the fuse terminals and then perturb the circuit at various places (or add circuit loads back on) until the breaker trips.  The last thing you did is where you focus on corrective action.

Do check battery terminals and the big cable connections for corrosion and low Resistance contact.  These will sometimes pass low currents (15A), but open when the 100 plus amps of the starter motor tries to go through the poor connection/corrosion.

It is actually easier to find faults in a dead circuit than an intermittant or a working one.  With a voltmeter, measure the voltage at the battery.  Note the value.  To check power routing, leave the negative test lead on the battery minus and use the plus probe to monitor connections along the power route that you trace from the wire diagram.  Easy access point are first, like the fuse clip terminals.  Fuse clip corrosion can wreak havoc on fuse reliability.  That why I pointed to previous posts about that.   An open circuit will be found when there is no voltage found where the diagram indicates a connection.  Jump back to a point closer to the batt source on the diagram to localize the area of the fault.  The Black wires on the bike are active when the ignition switch is on, and should have battery voltage.  This wire is general distribution for battery power.
Anyway, trace the power path from batt to destination device using the wire diagram and color codes as a road map.  But don't forget that a return path is required, too. So, if you find 12V at the destination device then continue probing the return path (Usually green).  However, now the fault is located when you lose 12 v on the meter.  The other way would be to leave the plus meter lead at the powered device and move the ground probe incrementally closer to the device until voltage is present.  When you get a reading again, you just skipped over the fault.

Sometimes, when probing, you find the problem just from mechanical disturbance.

You can also remove the battery connections and use the ohmmeter to measure for continuity between the battery terminal and the end device. The same progressive probing technique can be used to check integrity of each circuit on the bike noted by the wire diagram.

If you get confused with readings,  report what and where your measurements taken, and we can identify steps to pinpoint the problem area.

BTW, your charger can shorten the life of your battery even though it puts energy back in.  One teltale is if the battery gets hot during charging.  It will shorten the cycle life of the battery.  Just know it's not a connect and forget charger on your MC batt.  You need to standby and monitor temp and disconnect when battery warming or outgassing occurs.

Cheers,

[malcolmgb]

5 - a 15 amp circuit breaker?

I'm intrigued by the circuit breaker, where do I find one of these?

[TwoTired]

Circuit breaker source:

Local electronic supply.  Specify for low voltage applications.

Here's an quick but expensive source:

http://www.aircraftspruce.com/menus/el/circuitbreakers.html

I'm sure cheaper ones can be found at surplus electrical or some investigative online searching.

Circuit breakers are usually bigger and heavier than fuses, though.

Cheers,

[clarkjh]

Waytek has them, but I think they like big orders.  I had to regester my business with them just to get a catalogue.
www.waytekwire.com

James