Location of the Fuse Link on a 78 CB750

[Northern78CB750]

I'll keep my intro short, I'm a 28 year old truck driver, been wanting a motorcycle for many years, my father was a big Honda riders back in the 70s, loves to retell his cross country trip on a 73 Honda 750 Twin, and so this year I finally went out and found myself a nice 78 Honda CB750.  Good condition but the guy who had it, had torn apart the headlight assembly, the bike came with a Vette Farring on the front, so I think he removed it but then never finished the project, needed money and put the bike up for sale.  So I've been putting the lights back on the front.  Ended up shorting out a wire, blew the 15 amp main fuse, replaced it and got nothing.  Been researching and think I fried the Fusible Link.

So my main question is, where exactly is it or suppose to be, I almost want to say it turned to dust because I've traced the positive battery wire back to the starter solenoid, even pulled the solenoid apart, but I can't find it anywhere.  If someone could explain exactly where its is or suppose to be, or even a picture (be it of the link or a finger pointing to the location), it would help me a lot.  I was hoping to get her on the road this weekend but this no power issue has me stumped.

Thanks.

D.W.

[vern401]

There should be 3 fuses for your bike if I am right. One is a main fuse one is a headlight fuse and one for the tail light. check them.. they should be close to the sylenoid and rectifier behind the left side cover. Thats whear they are on my 78SS. The wiring is color coded in the headlight bucket. Between that and a wiring diagram you should be able to get it all going. I do not recal a fuseable link on them accept maby for the sylenoid. Most of them have been replaced with straight wiring by now. It will be a fat area on the hot wire going from the battery to the sylenoid and starter. I see them all the time in cars but do not remember Honda using them. If you have a test light it will help in finding your open circuit.  

[Northern78CB750]

Yeah in my internet research I can't really find anything that specifically says there is a fusible link / dogbone fuse on the bike, I did find one site that is selling them for 78 K8/SS but no specific literature.  I did find a full wire diagram which helps because there is no original headlight bucket that tells what wire is what for the lights.  The guy who had it before me was attempting to attach a dollar star Harley wanna be headlight bucket which I'm going to use to hold loose bolts or a plant, cause its just that horrid.  The bike came with a Vette Faring, so somewhere I'm guessing that was installed, and then someone removed it, thus no more original headlight.  I'm using the bucket off of the faring since it somewhat matches the original until I can either find an original or something better than the dollar store one that came with it.

The three fuses I knew about, the 15 / 7 / 5 amp right under the left side panel.  When I shorted the wire out, it blew the 15 amp main which I replaced but still had no power.  I don't see anywhere that there would have been or be a fusible link near the battery, I've traced the battery cable to the starter solenoid, checked inside the solenoid but then there really isn't anything to trace, as the main wire off the solenoid runs into a main whip and then back out into the starter motor.  There's two 14 gauge or so wires off the solenoid into another whip.

Either way though I'm going to pick up a test light and start tracing.  I'm also going to pull the fuse panel off since the connectors are pretty rusted up and give them a good cleaning.  Also got two buddies, one who has experience with Honda wiring coming over to check it out.  So hopefully I'll figure it out.  Thanks.

[Re-run]

Yeah there is no fusible link. You have the 3 fuses and that is it. You have a start with cleaning the contacts for the fuses, or you could find a small blade fuse box and swap out the old one. After that, your only other issue would be either battery or ignition switch. People seem to have issues with the ignition switch for 30+ years.
Check the connector for the switch first, make sure it has contact and is not melted or something.
From there, I would get a can of contact cleaner with lube for electrical switches. A can of that is much cheaper than a good honda switch.

[LukeM]

Back in the day when I used to work on electronics (TVs, musical instruments, etc), contacts would need to be cleaned.  One product we swore by (not at) is Deoxit D5.  It cleans the contacts, then lays down a conductive layer that resists dirt buildup.  Volume controls on amps that crackled like crazy settled down to dead quiet after an application of D5.  http://www.deoxit.com

Try to avoid contact cleaners that have any trace of oil in them.  Spray a bit on your hand, and see if it feels oily or slick after the cleaning portion evaporates.  If it's oil, you can count on dust and dirt building up eventually.  Spend a little extra, and get the good stuff.

Luke M

[Re-run]

http://www.crcindustries.com/ei/
http://www.crcindustries.com/ei/content/prod_detail.aspx?PN=03070&S=Y (the stuff I use)

This is the company that makes the stuff I use. It worked wonders band equipment too. Probably similar to the deoxit. You can get it with or without a protectant to prevent corrosion. I have not used the protectant version but another member here, woodsrider I think, informed me of it. So there isnt an oil and that is a good thing to point out.

Oil could make it worse and could melt the plastic.

[LukeM]

Yup, I've used the CRC products as well.  The nice thing about the Deoxit is you don't need a whole lot to condition the contacts. They tell you less is more, so use it as sparingly as you can.  The other manufacturer of cleaner solutions is Miller-Stephenson, but that's pretty high dollar stuff.  It does do a tremendous job, just costs somewhat more than the CRC and Deoxit.

Aside from that, +1 to Re-Run's comments.
Luke M

[Northern78CB750]

Thanks for the info, was the fuse connectors.  Didn't use any contact cleaning, just sanded them back down and got full power again.  Now my only electrical problem is the mess someone made of the front wires for the turn signals and headlamp.

I don't want to post a new thread for it, but could anyone recommend a good motor oil to use with the 750 SOHC?

[Re-run]

I use rotella synthetic 5w-40. It is a diesel oil that lends itself to motorcycles very well.

[jmark]

I ran into the same problem. Your answer solved it. Saved me a lot of time and money. Thanks