Topic: 1978 CB750K Electric Chaos

[BOANs88]

Ok so I just got a CB750K for my first bike.  Exciting right? Unfortunately I have hardly been able to ride at all because I have had all kinds of problems.
    My current problems listed chronologically and as separate occurrences.

-bike runs great for a couple rides
1-Bike won't start, headlight won't turn on battery tests bad
-buy new battery everything is fine.
-install new AM rear signals.
-crossed wires blew fuse, replaced it, corrected mistake, everything ok.
2-next day headlight won't turn on
3-following day headlight, neutral light, and new left turn signal won't turn on.
4-dying to ride I rode any way. Bike ran great for 7 miles to work.  On the way home it shut off randomly 5 times while I was riding.
-replaced 5a, 7-1/2a, and 15a fuse (modified blade fusebox) and nothing changed.

Battery sits at ~12.5. Gets to about 14 when revving.

Dying to ride the dang thing but thinking of setting it aflame instead.  This list of problems doesn't include a handful of others.  Any help would k d be appreciated.

[madmtnmotors]

Common ailments for any vehicle with a nearly 40 year-old wiring harness. Get a wiring diagram, voltmeter, and cleaning tools (wire brushes, files, sandpaper, steel wool, etc...). Roll up your sleeves and learn what makes these awesome machines tick. Takes me about two weeks, working evenings and weekends, to address every connector in the harness, switches included.

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

 My K8 has rewarded me with many trouble free miles. Often times the intermittent cut-out can be attributed to a worn out ignition switch.

[BOANs88]

I have the tools and the diagram, just havnt had enough time to put them to use.  Hopefully this weekend.  Your suggestion of the ignition makes sense.  I have a volt meter, but what setting do I use to test the ignition switch? I know this is a rookie question, but I'm without question a rookie.  Am I testing continuity on the ignition switch or measuring voltage?

[70CB750]

You check continuity to make sure the switch works and than voltage to see if you are loosing any in the switch.  Clean switch should be almost as good as plain wire.

Most of the time I use ohmmeter.

[flybox1]

+1 for the ignition switch.  clean it. 
grab some frosty beverages, sit by your bike with some tunes, and clean/treat/replace each and every wire and block connector you can find. dielectric grease is a good thing
also, bars turning left to right over 40 years can wear out wires.  inspect all wires and block connectors around the front forks.... inside the headlight bucket, too. 

[BOANs88]

What should I want when testing?

I unplugged the ignition switch From the bike.

On the bike side of the ignition box I have
-   -   -
- clip -

From across top to bottom Ohm reads:

13.4.    0.    9.2
9.2.     Clip. 13.4


But on the actual ignition switch it only had continuity on pins 4 to 5, and 2 to 3.

On my fuse box I had continuity between 5a left and right and all left pins.  But on 7a and 15a there wasn't continuity between left and right.


I don't know what I'm looking for so I am just posting as much info as possible.  Thank you for any help or educated guesses you can make based on this info.

Continuity on the bike side was good.  It showed continuity not between all ports but each port had continuity with at least one other.  That's all that matters right? Please bear with me, this was literally my first time using a voltmeter.

[calj737]

Replied to your post in the other thread....