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Author Topic: 1977 750F2 Ignition harness/switch testing and problem questions  (Read 5050 times)

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Offline bryanj

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #25 on: August 27, 2025, 07:02:12 PM »
Nothing to open up, just the contact part at bottom comes off the key part stays in one piece
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Offline scottly

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #26 on: August 27, 2025, 07:13:02 PM »
Quote from: sparker on August 27, 2025, 06:37:43 PM
Ready to open it up tomorrow and check it out.
I would just replace the switch part, as cheap as it is. ;) The "repair" in the video won't last long, as the contact has sunken down into the plastic from over heating. If you're curious, go ahead and take it apart while you're waiting for the replacement to arrive. ;D
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Offline sparker

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #27 on: August 28, 2025, 02:54:59 AM »
Quote from: scottly on August 27, 2025, 07:13:02 PM
Quote from: sparker on August 27, 2025, 06:37:43 PM
Ready to open it up tomorrow and check it out.
I would just replace the switch part, as cheap as it is. ;) The "repair" in the video won't last long, as the contact has sunken down into the plastic from over heating. If you're curious, go ahead and take it apart while you're waiting for the replacement to arrive. ;D
Yeah - that's what I was thinking.  It confirms that the "key part" is really not the issue.
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Offline sparker

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #28 on: August 28, 2025, 02:56:03 AM »
Quote from: bryanj on August 27, 2025, 07:02:12 PM
Nothing to open up, just the contact part at bottom comes off the key part stays in one piece
Yes - that's what I'm seeing which helps me to understand better - it has nothing to do with the whole column with the key.
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Offline rotortiller

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #29 on: August 28, 2025, 03:42:01 AM »
I had one acting up so I took it apart and soldered the rivet area at the wire connection contact stud. That was 15 years ago and it still works fine. Replaced another bike with an Emgo plastic unit and it still works great after 5 years.
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Offline sparker

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #30 on: August 28, 2025, 05:34:42 PM »
Took it apart & the new part is ordered! 
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Offline HondaMan

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #31 on: August 30, 2025, 11:49:07 AM »
Quote from: sparker on August 28, 2025, 05:34:42 PM
Took it apart & the new part is ordered! 

I've repaired several switches that way: they are all still happy and running today. :)
Back in the 1990s era, Honda only sold the whole keyswitch with seat lock as a kit for the late-model bikes like yours.
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Offline Don R

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #32 on: August 30, 2025, 12:13:48 PM »
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Offline sparker

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #33 on: September 02, 2025, 05:26:08 PM »
Just got mine in tonight!  Too beat to go out to the garage, but will be in in the next couple days.
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Offline sparker

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #34 on: September 06, 2025, 02:12:00 PM »
Well - it seems there might be something wrong with the new switch - continuity on/off iffy.  Hooked it to the harness - could get the power on and off.  Put it on the ignition key cylinder - nothing.  Take it out of the cylinder - no continuity turning the top knob. 
Wrote to Vintage CB750 to see about an exchange.  Maybe I just got a bad one.
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Offline sparker

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #35 on: September 15, 2025, 04:39:24 PM »
Well, got the switch up and going - took it for a spin tonight and everything was good - thanks everyone!
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Online newday777

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #36 on: September 15, 2025, 08:18:02 PM »
Quote from: sparker on September 15, 2025, 04:39:24 PM
Well, got the switch up and going - took it for a spin tonight and everything was good - thanks everyone!
What did you do to get it up and going?????????????
The post before you left it hanging.....
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 1 K2, 4 K6, 1 K8, 1 F1, 1 F3
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline bryanj

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Re: 1977 750F2 Ignition harness/switch testing and problem questions
« Reply #37 on: September 15, 2025, 11:56:29 PM »
Can i guess that the rotating bit was 180 deg out when you fitted the switch part
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!
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