New Battery causes starter to engage

[dragonfly888]

The 2 year old battery, on my 1966 CP77, died last week, so I ordered a MotoBatt MB9U. I ran the bike with this battery type for 8 years, so I thought I would give it another go.
When I try to install the battery, positive, then negative, the starter engages immediately, even with the key turned off.
Looks like there is a short somewhere and I am wondering if this points to the starter solenoid and/or the handlebar mounted starter switch?
If it is, indeed, a short, maybe this is why my old battery died!
Much appreciate if anyone has experience with this kind of issue and any pointers, tips or videos on how to diagnose and fix it.
Thanks very much for your help!

[Michael Stoic]

I doubt the new battery itself would cause this, as you suspect.

A common failure point for the wire harness (on many bikes) is the frame head wrap around. I would isolate and investigate/test that area first...

--
Mike Stoic

honda305.com/CP77/registry

[dragonfly888]

I concentrated on the Starter Solenoid...

I disconnected the two wires on the solenoid and removed it from the bike. Then I removed the two small screws holding the two halves together. Not having done this before, I was only able to open it up about a quarter inch, but the inside looked clean. So I put it all back together and secured it to the bike. I only put the wire from the battery back on, not the wire to the starter, then installed the battery. Now, when I turned the key on and pressed the start button, I heard the clicking in the solenoid. So I disconnected the negative on the battery, reconnected the cable from the solenoid to the starter, reconnected the negative cable on the battery and the system works fine now. Not sure why? Maybe there was a bad connection on the solenoid or maybe the starter switch assembly is intermittent?

[Michael Stoic]

A rule I find works well with diagnosing a problem is to retrace the preceding steps, where an inadvertent issue may have been introduced.

You may have something intermittent, or your now refreshed contacts re-established proper path to ground. If you suspect a potential of a run away starter, rig up a temporary quick disconnect for an emergency "eject" and keep it in play until you are confident the problem is eliminated.

--
Mike Stoic

[dragonfly888]

Thank you, everyone, for your help. The issue has not happened again, but there are other problems I am looking into... never a dull moment !!!

[Tim Allman]

I have had this problem before on my CB77 and, consistent with Michael Stoic's comment, it was up front. The wire leading to the starter button on the handlebar is live. The relay is activated when the circuit is completed (to ground) by pressing the button switch. Any place along the "Yellow & Red" between the relay and the button switch that contacts ground will cause your symptoms which often will occur at random.

I'm glad you have 'solved' the problem but I would want to check that wire from one end to the other so that this problem doesn't reappear while riding. My experience is that the wrapped sections of the harness are unlikely to be bad and it's hard to imagine how the wire could ground itself inside the wrapping anyway. Look at the central hole in the handlebar where the wire goes in and the right side hole under the switches where it comes out and connects to the starter switch.