Topic: 1975 750F Gauge (speedo/tach) lights flash with turn signals

[ryanGDanderson]

Hi there and thanks for your time/wisdom,

Tach/Speedo lights are off until I activate either turn signal, then they blink along with the flashers.
My attempted solution steps and notes:
1. Verified to my best ability that my wiring diagram was correct
- Perhaps I need to try again?
2. Found a post http://forums.sohc4.net/index.php/topic,36866.0.html stating to clean frame/engine/earth grounds
- About a year ago I had cleaned two mounts, one on the frame near the left coil and the battery -> engine/frame mount. Are there more that I missed? Should I clean them better?

Possibly related is that the front turn signal that is NOT selected still blinks a little bit. The back turn signals do not exhibit this behavior.

Info about bike:
The bike was sitting outside for up to 20 years before I acquired it. Regarding relevant (to my knowledge) electrics:
I replaced:
Wiring harness
Battery
Reg/rect
Blinker relay
Headlight - h4 LED
Taillight - 1157 LED
Indicator box bulbs - LEDs
Tach/Speedo bulbs - LEDs
Starter solenoid
Rear brake light switch
Ignition lock

I rebuilt:
All handlebar controls and wiring.
Fusebox, with new fuses

Issue occurs with either filament bulbs or LED, all in indicator light box and tach/speedo assemblies.

Thanks for your help, sorry if that was TMI

- Ryan

[Don R]

  Have you verified that the tach/speedo lights are tied into brown/white wires? 
  I have an F1 that I just re-wired but have not tucked everything into the box yet. I really don't remember which way the F instrument wires go, headlight bucket or wire terminal box, I can look next time I go out.
  Mine's a little different, I just wired in a K4 right control for the headlight switch/ start button. I like to be in control of the headlight, I'm an early 750 guy. L0L!   

[ryanGDanderson]

  Have you verified that the tach/speedo lights are tied into brown/white wires? 
  I have an F1 that I just re-wired but have not tucked everything into the box yet. I really don't remember which way the F instrument wires go, headlight bucket or wire terminal box, I can look next time I go out.
  Mine's a little different, I just wired in a K4 right control for the headlight switch/ start button. I like to be in control of the headlight, I'm an early 750 guy. L0L!   

Thank you so much for your reply! I have verified those connections, traced from gauges -> bucket -> fuse (where it turns into a brown wire to the taillight)

[Don R]

 My next obvious question was LED's? but you already covered that so that leaves those pesky grounds.
 Other things I've seen are powder coated handlebars not grounding, loose female connectors not making contact. (My PO had used oversized bullet connectors and expanded the female side)
  I like to run a ground wire from the connector in the headlight bucket to the frame by the coils and then to the battery connector. I also tie it into the green wire system somewhere along the way. 

[Don R]

 I reread your old post. Poor gauge grounds comes to mind.  I've traveled to fix a member's wiring issue before but an hour is my current range.   

[ryanGDanderson]

My next obvious question was LED's? but you already covered that so that leaves those pesky grounds.
 Other things I've seen are powder coated handlebars not grounding, loose female connectors not making contact. (My PO had used oversized bullet connectors and expanded the female side)
  I like to run a ground wire from the connector in the headlight bucket to the frame by the coils and then to the battery connector. I also tie it into the green wire system somewhere along the way.

Don R thank you for both of your responses. I live in central florida FWIW. I would love to wire a ground directly because I've never been a fan of frame/engine grounds, I've just never researched the proper/clean routing, if there is one; I just don't want a hacked bike.

I kept the turn signal bulbs filament for now. They're bright enough and I don't feel like spending the time to do the conversion yet. I've seen that the flasher "idiot lights" could introduce problems when switched to LED but filament bulbs didn't change anything.

To your other point: I didn't powder coat the handlebars but I did spray paint them. I wouldn't be surprised if that introduced insulation, I did not know the handlebars were a part of the return.

[ryanGDanderson]

I have re-checked and re-cleaned the frame ground next to the ignition coil, and I have also ensured the two handle bar mounts are metal on metal (no paint). Still the same flashing issue though

A few more points of interest:
1. Is the turn signal switch box, and/or starter switch box, itself grounded on the handlebar? Those sections of my handle bar are still painted.
2. I found that my charging system is not working, by proxy of battery leads show low voltage as well as no voltage change at any RPM. I disassembled, cleaned, and tested the alternator assembly and found no faults (ohms in range, continuity in all wires). Could this be indicative of a faulty ground somewhere on the bike? I expect to do further testing on the charging wires when I reassemble (waiting on gaskets).

Thanks everyone for their time and attention.

[Jerry Rxman Griffin aka MuthaF'er]

My original harness Jan 75 build utilized a "special" jumper that connected 2 male leftover leads that did not color match. This was discovered after all the other color matching connections were made. I believe it was part of the wiring connector box at the down tubes. Been a long while....

[HondaMan]

Hey, that's pretty cool! If we figure it out, making the speedo flash with the Left turn and the tach with the Right turn might be helpful in reminding to turn them off?


But..it sounds like the grounds aren't. Often (in Florida bikes I have worked on, including most recently a nice F1) the ground to the headlight bucket (those headlight ears) are impaired in the bikes from wet/salty climes. On the last one I fixed, I had to physically remove the headlight ears, the handlebars, and the handlebar switches, and clean all their contact surfaces. Afterward I added a drop of LPS-1 (not LPS-2 or LPS2.5 or LPS-3) to each site to ensure they won't do it again. On this bike, one side's turn signals only came on in back, while the other side would come on at both lights and the dashboard, but would not blink. After the cleanup, all worked fine again.

This particular bike had the tapered steering head bearings (I had installed some 10 years ago on it) so the forks grounded well to the frame. In another 750K3 that came from Lighthouse Point, I could jumper a wire to the headlight from the under-tank frame ground and make everything work, so I told the owner to change out the (rusty) steering head balls/races or install the tapered type, which he later did, to fix it. On this bike, the turn signals would only come on (but not flash) when the headlight was on LOW beam: on high beam they went out. Poor grounding in the forks and headlight cause most of these problems.

[ryanGDanderson]

Thank you both for your thoughtful responses.

My original harness Jan 75 build utilized a "special" jumper that connected 2 male leftover leads that did not color match. This was discovered after all the other color matching connections were made. I believe it was part of the wiring connector box at the down tubes. Been a long while....

I will try to jump the hanging connectors in my lower jbox and report back.

Hey, that's pretty cool! If we figure it out, making the speedo flash with the Left turn and the tach with the Right turn might be helpful in reminding to turn them off?


But..it sounds like the grounds aren't. Often (in Florida bikes I have worked on, including most recently a nice F1) the ground to the headlight bucket (those headlight ears) are impaired in the bikes from wet/salty climes. On the last one I fixed, I had to physically remove the headlight ears, the handlebars, and the handlebar switches, and clean all their contact surfaces. Afterward I added a drop of LPS-1 (not LPS-2 or LPS2.5 or LPS-3) to each site to ensure they won't do it again. On this bike, one side's turn signals only came on in back, while the other side would come on at both lights and the dashboard, but would not blink. After the cleanup, all worked fine again.

This particular bike had the tapered steering head bearings (I had installed some 10 years ago on it) so the forks grounded well to the frame. In another 750K3 that came from Lighthouse Point, I could jumper a wire to the headlight from the under-tank frame ground and make everything work, so I told the owner to change out the (rusty) steering head balls/races or install the tapered type, which he later did, to fix it. On this bike, the turn signals would only come on (but not flash) when the headlight was on LOW beam: on high beam they went out. Poor grounding in the forks and headlight cause most of these problems.

This seems reasonable to me, and I would like to test before tearing it down. I have have confirmed continuity from both headlight ears (though from the external side of the bolts) to the black battery terminal. If that is not a valid test, then is it reasonable to say that I can test by jumping one or both in-bucket ground collectors to a known functional ground on the frame or engine?

[ryanGDanderson]

Hi all, just posting to wrap this question up: I simply had a powered wire or two connected to the wrong collector(s). The other topics I wrote about were seemingly unrelated. The solution was to go thru the wiring diagram 10 million times until I got it right. Sorry for the chaff

[newday777]

It's good that you found the problem and have fixed it. With all the wires tucked in the small space it is easy to mess up.