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1974 CB750 First Bike, First Problems

smscamaro

CB750 New member
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I just bought my first bike.

It's a 1974 CB750 with 4200 miles.

I have a few wiring problems so far.

I can't get my running tailight and running turn signals to work. I'm getting no power to the wires (I've only traced it back about 2/3 feet) The brake light works.

And

My left blinker is slow and stays solid when the headlight is on.

Any Ideas I would be happy to hear, I'm pretty clueless when it comes to wires.
 
A good majority of the electical connections are in the head light bucket. They have a tendency to get loose or pull part way apart over the years of riding. I would pull the headlight and look for obvious loose or disconnected wires there first. There should be no reason for headlight to affect blinkers so I would bet there is a ground issue somewhere. It is really hard to fix electrical problems over computer, I would strongly suggest getting a shop manual or looking online for a wiring diagram, then you will know more about how the wiring is laid out.
 
I think I just pooched my wiring last weekend. I tried switching the handle bars for more aggressive/lower bars (not quite clubman) and the cabling / master cylinder wouldn't fit well, so I ended up putting my old bars back on until I can get a shop to look at it. But, then when I was wiring up the electrical in the headlight bucket I couldn't get the headlight to function. Everything was going well and the electrical was all working, but then it all died. When I turn the key no more electrical / zero. Is there a fuse or have I blown a relay or something? Does anyone have a good wiring diagram to share?
 
Yes there are fuses under the left side cover. If you google or some other search for cb750 wiring diagrams there are a ton that come up. Specify the year though because there are differences.
 
lol, yep your right just searched for diagrams and found a bunch. I'm going to tackle this again on the weekend. I'm sure I must have blown a fuse, so I'll check those too.
 
CB750 Member

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Spark Plug Wires from a new guy
I'm new to this site and to bikes in general, I know my way around a paint gun and bodywork but the mechanicals of the bike is another story. I recently picked up a 1975 750K5, hasn't been run in years, though the PO said he had it started a few months ago. yet when I checked in the tank the old familure varnish smell cam pouring out, it had 2 plug wires disconected from the caps, incorrect tank with the petcock on the right side verses the left, not hooked up to any of the carbs. and no air cleaners on the carbs, and the carbs. were frozen. I lubed up all the linkage and freed up the carbs. and choke linkage. This bike has been setting a long time, and the fork sticker was last inspected in 1989. Kicks over fine, the proper tank came with the bike, as well as another engine and bank of carbs, and small parts. This is my delima, when it comes to coils and plug wires, the NGK caps look good, and the wires might be good, but how do you assemble the wires to the cap? I notice that inside the cap is a copper barb, do you expose some of the wire core then push (twist) the wire down over the barb tight then slide the rubber boots back over cap/wire. The coils have fixed plug wires, I found a nice set of coils and wires for a 97' 750 nighthawk with removable wires, will they fit? I know the points coils are 5 ohms and elc. ignition coils are 3ohms. There is also some NOS Honda sets but they are double $$ the used coils. I read that with heat the plug wires cores will tend to become gummy, the wires on the bike are a bit soft. Any tips for the uneducated? I've got a new battery, plugs and will clean and set the point gap, as well as check the compression. I just want to see if she will come back to life!!
 
jbird, I commented on your other post. There are some other posts of people starting up bikes that have sat for a long time, might find something on the older posts that I may have forgotten on this post.
 
Just a follow up post to my wiring problem, I definitely had a blown fuse. 3rd down 15amp was broke. I replaced it and got most of my electrical back up and running following the diagrams I found on the web. But, still can't get the bike to fire. I know its still my wiring that's holding me back. I currently don't have the gauge lights, the tail license plate light & most likely the kill switch. The headlight, turn signals, horn and ignition all work - I tried to start the bike, but it won't fire. I pulled one of the plugs out and held against the head while starting and I get no spark. Hence my wiring problem.... ughh
 
check for 12 volts at the coil wire the black/white which is the power feed for the coils. Power goes from the a splice in the headlight bucket to the kill switch then to the coils. If you have power then you have a point or coil problem if you dont then its the kill switch or no power to the kill switch.
 
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