wireing 78 CB750 SOHC need help

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wireing 78 CB750 SOHC need help

bomber737
I replaced the wireing harness on my 78 CB750 and I am having one heck of a time getting things hooked back up.  Is there anyone on this site who would be willing to take some pictures of the connections inside their headlight bucket and the turnsignal flasher relay.  Or if there are any cb members in the st paul mn area that might be willing to stop by and give me a hand getting this completed.  I would be greatly in your debt.  Lunch is on me.  

Thanks in advance

Bomber
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Re: wireing 78 CB750 SOHC need help

Piute
 


Simply follow the color codes on wires along with book looks like it's hard with it all messed together like they are ,But just think of it a wire at a time and clean as you go and get started,I've completely gone through my bucket a few times due to using a faring and customized another.

http://www.oregonmotorcycleparts.com/diagrams.html

                            1977 CB750 F2 Super Sport
<LET THOSE WHO RIDE DECIDE><RIDE TO LIVE-LIVE FOR JESUS> 
Native American from central Cal,  Kickstand UP in S.W.Missouri,
                                       
 
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Re: wireing 78 CB750 SOHC need help

bomber737
I have that diagram and I have scaned it in and blown it up so its easier to read and follow.  My problem is someone cut the connector off the left side control. I have a spare connector so I an re-attaching wires and the colors in the brand new harness and the old control are close but still a little off color.  There are also seems to be a black wire that comes from the ignition tht supplies switched power to all the lights and controls.  I am also confised by all the green wires that have multiple female connectors.  I asume they are just a common for all the lights and such but 1 of them must run to ground.  This is the reason I would like some pictures of the connections.  I have been having my father help me (he is a retired electronics engineer) so he is very experienced with this kind of stuff.  Thanks for the help though.  Ill keep pluging away at it.  

Bomber
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Re: wireing 78 CB750 SOHC need help

Piute


     Your right what a mess,all thoughs Grn.ground wires,I eliminated all in front of bike that I could find start N finish ends used 1 heavy ground to a grinded frame cable ground connected to frame under tank.
   With all the aluminum and rubber mounts they have to use each and every wire,They just "ARE" old and need some attention be sure to use the Ole elect.grease as well,on every connection,work with military conections everyday Possitronic Ind.
      Those Blk.wires were my prob ,cause I thought they were grnd's. You can tell how they a grouped together ,Try to keep them in the same/right group,shorts would be easyer to find later if needed by doing so,. Keep going there is light at the end of the tunnel.
                            1977 CB750 F2 Super Sport
<LET THOSE WHO RIDE DECIDE><RIDE TO LIVE-LIVE FOR JESUS> 
Native American from central Cal,  Kickstand UP in S.W.Missouri,
                                       
 
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Re: wireing 78 CB750 SOHC need help

TOOLS1
Administrator
In reply to this post by bomber737
The greens are all grounds, and connect together. There will be several that are not used, so don't worry about having extra female connectors. Also out of my 7 CB 750's none of them have the stock wiring intact at the headlight, just modified the last original one I had a few weeks ago, so as long as everything works, your good to go.
TOOLS
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I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
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It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
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1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Re: wireing 78 CB750 SOHC need help

Thorby
I still need to study the wiring diagram and figure my wires out because I have bunch of electrical issues: main fuse burning every couple of months, blinker not blinking, stop light signal not working, right blinker randomly going on and off as if a loose wire.

Why do motorcycles have such a mess of wires?  TOOLS mentioned some are not even used.  What's the point of this?   And apparently age is not related, a buddy has a cheap 2010 Chinese 150cc commuting bike and he recently reported the same wiring mess including unused wires.

Oh, well.  At least it'll be a lot of fun figuring out my electrical system.  I'm a bit lazy to work on the bike on my own, but I am motivated to figure this part out because it will come in really handy if I ever get stranded on the interstate.
Proud owner of stock '76 CB750.
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Re: wireing 78 CB750 SOHC need help

shinyribs
Administrator
Fuses suck. I know I will catch flack for this,but here goes. I run fuse-less. Unless a wire gets pinched and dead shorted to ground it'll never burn up. You just gotta protect/tie your wires up real nice.Which you should do anyway.

 I was sitting on the starting line one day,final round of a $3,500 bracket race and my fuel pump fuse died from vibration alone. I had that race in the bag 100% I hate fuses. Of course,run fuseless at your own discretion.
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Re: wireing 78 CB750 SOHC need help

bomber737
Well I did manage to get the horn working so I have that covered.  Now I can make engine noises with my mouth but i don't have to pretend to honk the horn.  What makes no sense to me is that there are black wires coming out of the ignition that have 12VDC so I am figuring that's where all the power to run all the other stuff i.e. lights, turn signals, left and right side controls, headlight get their power from.  It seems all this stuff ties together with the green wires as a common.  i tested the green wires and they all have small resistance values suck as .1 to .2 ohms so I know the power is going through a light bulb.  What I need is a 2' x 3' enlarged and colored wire diagram that is legible.  And I still can't figure out how the wires attach to the flasher relay.  I am using a solid state 3 pole flasher relay since that what I had but id does not seem to want to work. If I hook it up one way it buzzes, move the leads and it buzzes and the third way it does nothing.  Perhaps the old Honda one handled more power and this one just doesn't like it.  They are never marked so a caucasian can figure it out.  I also replaced the stock fuses with a rewired spade type and it looks great, very clean. Now I even have spare fuses right where they blow.  
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Re: wireing 78 CB750 SOHC need help

Piute

      Lil Story,
   1 of the guys gave me some L.E.D. lights that I hooked up to the rear (replaced stk.) Had them working great,(for me) ,I then went to put the same up front,couldn't wouldn't workseem to mess up the rear I just got right(so I thought),SO called in the PRO(cuzz.Paul) He looked at the rear and ask how I got running & winkers with just 2 wires from the new L.E.D.s.(some how I hooked them up and they worked the way I wonted)HE did a few thingy's with tester(witch I don't no how to use,just the basic power/no power test) THIS / THAT what I was talking about earlyer about those dang BLK.wires,had one not in use ,ALL HAS TO BE according to book on some of the wires..................THE END>>>>>>>>>>..


                            1977 CB750 F2 Super Sport
<LET THOSE WHO RIDE DECIDE><RIDE TO LIVE-LIVE FOR JESUS> 
Native American from central Cal,  Kickstand UP in S.W.Missouri,