Topic: Honda CB750 Wiring

[Deltarider]

Yep, that's how it is supposed to look. The blue HB one can hardly be noticed in daytime. The red oil pressure one can sometimes flicker at idle, but must go extinct when revved.

[MauiK3]

I re-harnessed my K3 750 when I took it down to the frame. The harness was pretty stiff and I felt it would let me down. It really wasn't too hard, there are sketches and photos of where the harness is supposed to be, take pictures too (if you decide to put a new one in). Yes, the headlight bucket is the hidden mess but it's not that bad. My glitch was the safety switch mine came with. I eventually just bypassed it, it's not needed here.

[kyle750]

gauges - old school analog simplicity - easy to read needles and numbers

[Jerry Rxman Griffin aka MuthaF'er]

Many of us install an oil pressure gauge in the "port" on the right side above the ignition cover. Looks like one of the covers in the valve cover to access adjustment of the valves. This gives you an actual indication of the real oil pressure.

How you exactly test the pressure switch, which is at the rear of the cylinder block on the upper case, dummy light I can't say for sure. I believe when pressure drops it switches on and supplies current to the light. It will not give you an actual pressure reading like a gauge and is only designed to come on when pressure is at or below ~ 10psi so you really do not know a current oil situation and if something catastrophic occurs, potentially too late. I like the combination of both.

[kyle750]

Many of us install an oil pressure gauge in the "port" on the right side above the ignition cover.

Thanks Mate.  I can see why an added auxillary oil pressure gauge is important.  Decided to buy the Marshall oil pressure gauge.  The white face is probably easier to read but went with the black for a more vintage look.    Looks easy to install with pipe tape wrapped around the threads.

[BenelliSEI]

Kyle….. I use these on my bikes. Very reassuring to glance down and see the needle where it belongs!

Make sure you put the original cap in your tool kit, along with a wrench that fits them both. If the bike ever falls over that gauge will get snapped off and you will be stuck…..

[kyle750]

Kyle….. I use these on my bikes. Very reassuring to glance down and see the needle where it belongs!

Make sure you put the original cap in your tool kit, along with a wrench that fits them both. If the bike ever falls over that gauge will get snapped off and you will be stuck…..

Excellent idea.  Always be prepared.  Thank You!

[kyle750]

How to measure progress 

When I first bought the candy gold CB750 Tony came over and looked at the bike and his response when first seeing the bike was simply "Das ist Scheiße . . .  Every part is Rusted."  I asked about a particular part and he responded "Who cares . . . you're never going to ride the bike"

Now one year later at lunch I tried to explain my understanding of the overspeed warning indicator light to him and he said very easy to check but  "Who cares . . .  you're never going to ride the bike over 80 km per hour"

Notice the difference?  The slow and steady progress of the slow-witted tortoise 

[kyle750]

When I mentioned about adding an oil pressure gauge Tony rolled his eyes.  In his opinion adding a gauge to alert you to an oil pressure problem is not a very good idea.  Replacing an original, heavy duty Honda plug with a cheaply made gauge that can fail in multiple places defeats the intended purpose. You are monitoring for a potential problem but at the same time increasing the risk of creating the exact problem you are trying to monitor - an oil pressure problem.

Also looking down at a pressure gauge while riding adds the additional risk and danger of not keeping your eyes on the road. Similar to a red blinking overspeed warning light - both are unnecessary and distracting.  All very good, valid points.   I'm sure there are many different opinions on the matter. 

[Deltarider]

There's no need to install an oil pressure meter. Ask yourself: what's the use of such a meter in the event there's a sudden pressure loss. It means that in order to catch that extremely rare event, you would have to have your eyes on that meter constantly. A distraction you can do without, if you're interested in safe riding. IIRC occasionally measuring the oil pressure was done by a Honda mechanic when there was some suspicion and certainly not more frequent than every 20.000 km, if ever...
Installing one yourself always brings the risk you make an error. Sometimes a leakage will develop and I have also seen pressure senders that were in a spot where they could easily be damaged by just manoevring your bike in a garage or in between other bikes or after falling over. You will never forgive yourself for a leakage of your own making.
An oil temperature meter can be useful however, but then one that's in the view of the rider and not - the horror! - some gadget near your right foot.
Inspired by some small, clever and cheap LED voltage indicators, I've suggested a similar small LED thingy that can show blue, orange and red. It would be: blue to indicate oil temp has not been fully reached, say: < 80^oC, orange from >110 - 120^oC and red when over 120^oC and ofcourse extinct when the oil temp is right. In daily use the blue go extinct is the best such a thingy offers.

[MauiK3]

I have an oil pressure gauge. It's sort of a pacifier, I glance once in awhile at idle when hot and at road speed just to be sure the pump is working correctly inside my 53 year old engine humming away down there. It's reassuring is all. Also looks cool :-))

[BenelliSEI]

I have an oil pressure gauge. It's sort of a pacifier, I glance once in awhile at idle when hot and at road speed just to be sure the pump is working correctly inside my 53 year old engine humming away down there. It's reassuring is all. Also looks cool :-))

Agreed. I like to see it pop up on startup and sit a a rock steady number when going down the road. Works for me.

[kyle750]

Bringing the CB750 wiring project to completion

Many Thanks for all the assstance and advice. Passing light and horn have been checked and are working OK.  I also forgot to check the parking light in the ignition switch and it correctly turns on the rear running brake light. I am quessing that if the parking light is left on for few hours the battery will be drained and possibly dead. Old wiring in the electrical panel has been cleaned up with new heatshrink tubes, voltage rectifier coupler has been relocated to the correct mounting bracket, and new NOS Honda dangling fuse has been added and mounted to the correct tab.

I understand that the overspeed warning and parking light were added for additional safety measures but IMO they are not necessary.  I also moved the handlebars rapidly from side to side and as far as they would go to to check for any possible wiring problems in the handlebars.  No issues so good to go! 

[BenelliSEI]

Have a good look at the two leads to the brake light switch on tha front tree. As they age the outer shield gets very brittle and turning full right pulls the wires off the switch. Make sure there is plenty of slack there.

[kyle750]

Have a good look at the two leads to the brake light switch on tha front tree. As they age the outer shield gets very brittle and turning full right pulls the wires off the switch. Make sure there is plenty of slack there.

Thanks Mate.  The outer shields on the two leads on the brake light switch are indeed very old and brittle.  I put new shrink tube on the wires leading to the brake light switch and will make sure there is plenty of slack.  It does looks like any movement there could easily pull out the leads.   

[kyle750]

Have a good look at the two leads to the brake light switch on tha front tree. As they age the outer shield gets very brittle and turning full right pulls the wires off the switch. Make sure there is plenty of slack there.

Just doublechecked the brake light switch wiring and you are absolutely correct.  When turning the handlebars to the extreme right there is considerable pulling of the wiring and old plastic shields. Connections definitely want to pull out of the switch and the wiring bends the shields into a weird angle. I am quessing that the previous owner had the exact same problem as you mentioned.  At some point in time about 12 cm of additional wiring was added to the exisiting Honda brake light switch wiring coming from the main harness.  Actually way too much extra wiring  so I had to push most of the slack back and tucked it behind the center stem.

In addition I wrapped the 2 wires in loose shrink tube to tidy it up a bit.  I also cleaned the switch bullets and tightened the female bullet connectors in the wires. Very solid, tight connection.  As an added precaution I just pulled out about 4 cm of additional slack and let the wiring bundle dangle a bit. Plenty of extra slack in place now. Thanks again for sharing your experience and knowledge.

Photo taken with handlebars turned to full right

Late Edit:  Shiny new front fork chrome trim rings.  An expensive NOS part but really finishes off the look of the front forks   

[MauiK3]

The triple tree and steering neck paint appear to be in good shape. Keep an eye on the brake light switch, being old, you wouldn't want it to fail in any way.