Engine will only start with handlebars to the left [80 CB750 Custom]

[Kajpaj]

Hello folks!

Just as the subject states, the bike will only start if I point the front wheel to the left. Initially, I had a range on the left side where the engine would start but now I have to point the wheel all the way to the left. My best guess is that there is a worn-down cable somewhere in my harness between either the clutch, starter or kill switch and the starter relay switch.

Has anyone here has experienced similar issues?

 

[pidjones]

Help us here. Won't crank, won't fire, no power at all? Does pulling in the clutch help? A few more symptoms would help. I've had a single wire in the bundle to the trunk lid on my GoldWing take out the remote lock function. You should probably have a bundle down the left side of the steering head. One of the wires in it opening. How to tell? Since it is probably inside the insulation, it will require flexing each one individualy feeling for the break, or running jumpers until things work.

 

[cxman]

the clutch wire and kill switch wire meet in a solderjoint in the wiring harness just behind the part that spans the frame to the forks

the wire is broken at the solder join so its only making contact when you squeeze thhem together

you will have to untape the harness find it i usually bridge the break with a very short piece of wire solder and heat shrink both ends

and tape it all back up this also happen on a lot of the cx500s

 

[Sonreir]

Alternatively, it could be loose wiring leading up to or into the main switch. Are you noticing any other electrical issues or just the starter button?

 

[Kajpaj]

Hello folks, thank you for the responses.

Before going down the symptoms, this is a bike that last ran in 1990, I basically bought it in pieces, so it is by no means in running condition, I did a top rebuild replacing piston rings, lapping valves and adjusting shims, etc.

I got the engine to run a few weeks ago but my job schedule has prohibited me to work on it, at the time I left it the engine was only running with choke, did not run evenly at low RPM (>1500) and the engine would not drop RPMs with the throttle down(this is a problem for a different post).

Fast forward to last week when I tried to start up the engine, the engine would only turn when I pressed the starter button, pressed the clutch in and turn the front wheel to the left. Please note that previously the engine started and RAN while the front wheel was turned to the left and while running I could turn the wheel.

@cxman, I could not locate the joint you are mentioning, what color are the cables?

@Sonreir, I am not noticing any additional issues but again, the bike is in pieces, also, what do you mean by the main switch? ( I assume noobie question)

Thank you all for trying to help, much appreciated!

PS. I would love to connect with someone local in the Bay Area (San Fransisco) that either owns a CB750 or is very familiar with my bike that I could buy a beer and pick their brain.

 

[Kajpaj]

Alright, folks,

Finally got some time to work on the bike today and a little bit yesterday.

Yesterday, I soaked all the connectors of the wire harness in vinegar to clean them up and after reconnecting everything voila, the engine would turn when the front wheel pointed in any direction. However, after about 10 min, it reverted to only working with the wheel to the left again, my theory is that one of the connectors might have a loose wire or something.

The current plan is:

1. Short the green and red wire directly to the ground at point 1 to circumvent the clutch circuit, then I will try to get the engine to turn and hopefully I will get an indication if the clutch is the culprit.

2. If the clutch is not the culprit I will connect point 2 directly to the battery after reconnecting the clutch circuit.

Hopefully, I will not short something to badly and set the bike on fire....

 

[Sonreir]

Main switch means the ignition switch.