Topic: CB750 no start NOW FIXED!!!! OOPS needs fixing again

[CAPTRON]

 I hope some one can help.

I have a 69 cb750 with a 74E eng and
wiring that is just giving me
fits. I bought this bike from a guy who bought it from another guy
who...you get the picture. It has not run since 1985. At least that
was what I was told. I went through checking everything out. I bought
a new battery. At first it turned over no problem. It turned over
several times with spark plugs in and with them out. I went to do a
compression check and none of the lights would come on. I could jump
the starter and it worked, of course it would not start. Fuses all ok.
Pulled wires and checked things. Everything seems ok except that when
I put + 12volts[I have 12 volts at the key switch] to ign on back of
key switch, sparks fly and no lights come on. I know this is not right
because one time I checked it, lights came on without a lot of sparks.
I was then able to start it up. This might just be out of the blue but
my headlight is burned out on low and high also. Do not know if it
came this way or not. It has sat for two days while I tried to check
out wiring. Then out of the blue today when I turned the key lights
came on. Got it running. Rode it for 9/10 of a mile and pushed it 3/10
of a mile back home. Same thing. Turn key and nothing no lights.I
figure it must
be some kind of modual [ starter motor safety unit,relay switch, etc.]
that is grounding out. But which one. I have never
heard of this before. I should add that I was given a Honda manual
with it that had the electrial section stickyed. The guy I got it from
did not try to get it running before I bought it from him. No telling
how long this has been going on.Can some one help me out? Thanks, Ron
u s 2 2 g o @ adelphia.net take out the spaces.

[mrblasty]

The ignition switch may be screwed up, You can get these for around $25.00 and confirm the harness is hooked up correctly,
You will need to confirm that all of the connections are clean and making good contact.
good luck

[dusterdude]

hey ron,glad to see you took my advice.you`ll like it here,good bunch of guys just look out for that k8 bunch.

[TwoTired]

If you aren't blowing fuses then it seems likely you have an intermittant connection somewhere.  This could be in the wiring itself, the interconnects, or the switches, etc.

To avoid flail and make measured progress, I recommend getting and inexpensive multimeter (under $30) and methodically follow the voltage from the battery terminal throughout the wire harness to known destinations exemplified by the wire diagram.  With the key on, progressive probing may just wiggle the right part to where your lights come on.  Then you know that whatever you are wiggling has the problem you are trying to solve.  Could easily be something like the ignition switch internal contacts.  But, if the problem is elsewhere, the meter is freind, especially if you get pointy probes capable of piercing the insulation of wires.

Cheers,

[mrblasty]

Oh Yeah Those k8 fellas are a breed of their own, If they offer you easy cheese pass on it

[CAPTRON]

YEA!!!! It took me awhile but I finally found it. I figured it was something grounding out. I thought that it might be a starter switch or something along that lines. I finally broke down and unhook everything and went wire to wire untill I finally found it. Total time it took me was about 4 days. Mostly because I drugged my feet not wanting to have to check out every wire. Anyway, it turned out to be two of the idiot lights had grounded out  on the holder for them. The rubber had  rotted away and allowed them to ground out  at different times. Sometimes one , two or both at the same time.

Now comes the fun part. I have not decide yet which way to go with it. I leaning towards just fixing it up as an everyday rider. It's too bad that someone in the past changed the eng and wiring over to 73 or 74 since it was a 69 sandcast to begin with.  Of course I always wanted a cafe style bike but I am 53 and my body won't like being bent over like that , still......

Thanks for all the help, Ron

[mrbreeze]

Hey Ron,glad to hear you got er all sorted out.Intermitent is the worst nightmare out there.I think it is better to to go through it at home and correct problems (or potential problems) than out on a weekend putt hundreds of miles from anywhere. Oh and Dusterdude...Yeah...them K8 guys!!!!

[dusterdude]

uh huh

[CAPTRON]

OH NO MR.BILL NOT THAT

New wiring problem..... or operator error.

Well things were going just fine right up untill that big woosh. Then lots of heat and smoke.... Oh did I mention flames?? Gives new meaning to "arse on fire".

I guess you can say I was too eager to see it running. I really really ment to change those old fuel hoses...... no choice now.

Have you ever seen flames coming out the top of your tank before?  Well when a tank gets warm it vents gases out the top. When introduced to a flame... like bike being on fire.... it shoots them straight up about six feet or so.  Another thing is how fast this can happen. 
I am so amased at how much flames and gas can be shot out of a carb. I just checked it out... eight feet!!! Well at least I had it outside the garage and not in.  Although it seems now , still not far enough outside as it manage to smoke the underside of the eaves and fill the garage with so much smoke it took all most a  half hour to clear it out with a commercial fan.  Oh and that 8 feet could have been more except it was blocked by hitting the side of the house.... not before burning my wifes plants that were in the way. It was more like a flame thrower.

I can tell you that I did not panic...well not a lot .....  as things raced through my mind.  Things like .....gee the fire extinguisher is empty and the fire is getting bigger.... do I have time to get the water hose  before A] the house catches fire B] my charter boat catches fire or C] those four  5 gallon jugs of gas left over from the hurricanes not more than a foot away goes boom and D] will I be a live so my wife can beat the SH**T out of me for being so dumb.

Here is the " I can't belive it". The wiring is still "good".... well as good as can be expected for being set on fire. Lots of heat damage but everything still works. I have a a 750 super sport that I can raid parts off of as the gears are no good. So things are not as bad as they could be.... I think I just heard my wife scream something about her flowers... got to go now.

Ron