Topic: 1977 750F2 Ignition harness/switch testing and problem questions

[sparker]

Help!
I've been going through the old posts and getting some answers, but the solution is still evading me! 
When I turn the key, I'm not getting any power.  This has been an issue in the past the I linked to the ignition harness/switch under the handlebars.  A little wiggle and it would come back or go out.  After, reading, I decided to use clip ties to make the whole more solid and it seemed to work for the most part, (after cleaning up the plug - female and male connectors). 

Yesterday, I wanted to go out for a ride - nothing.  Wiggling did nothing.  I disconnected the plug, sprayed the connection and tried again - no luck.  I checked the fuses - current on both sides of the 15A.  Checked for current at the red wire plugged into - current as well.  But when I checked the black wire at the plug, which if I understand right, should go to the ignition - nothing.  Nothing at any of the other three brown wires either.  (Maybe I can mention as well, I've not been getting electricity up to the instruments bulbs either although still had the warning lights and was able to ride last time,). 

So I unplugged the connector again and tried a continuity test between the red and black male connectors with the key turned on - nothing.  Shouldn't the key, with the switch flipped to run be creating a circuit?  Not sure where I should be going at this point.

[scottly]

If you have 12V going into the key switch on the red wire, and zero volts on the black wire with the key turned to the first position, the switch is faulty. If you put a jumper between the red and black harness wires, everything other than the taillight should work. Remember to remove the jumper when done testing so you don't drain the battery.

[sparker]

Did the test as you suggested Scottly. 
Got 12V at the red wire with the key in the first position.  Nothing at the black.  I didn't jump them, because I figured that this was all I needed to know.  I see the replacement switches for sale.  I'm understanding that I should be looking at a relay as well since they don't seem to be made to take the amps from the 750?

[scottly]

I would see if I could repair the stock switch first.

[sparker]

Not quite sure where to go with the stock switch.
Has no continuity on the first position between the black and red male connectors.  No amount of wiggling seems to work.  Cleaned everything with contact cleaner. 

[newday777]

Not quite sure where to go with the stock switch.
Has no continuity on the first position between the black and red male connectors.  No amount of wiggling seems to work.  Cleaned everything with contact cleaner.

Pull the switch out and open the bottom up to see what needs attention
Emgo made switch bottoms for a while, they might still be available.

[sparker]

I'm going to give it a try!  I see I can get the switch repair kit - which is essentially the bottom part.  But I'll have to open the faulty one first. Thanks for the suggestion!
Question:  if I just have to replace the bottom part, will I still have to deal with the EMGO amperage issues or would that have no effect on it?

[scottly]

I had a problem with my K1 switch, where the bottom part wasn't held tightly against the main body so the contacts weren't pressed together by the spring. There was no way to re-crimp the thin metal piece onto the main body, and the "tabs" on the thin metal piece that held the plastic part were damaged and broken, so I clamped it together and used JB weld to glue it all together. I think that was 10 years ago? BTW, the contacts themselves were in very good condition. I don't know if your switch is made the same way? Please post a pic or two. 

[sparker]

This is a pic of it in under the handlebars.  I had had some problems with it cutting out last summer and read some other suggestions in the forums and ended up using quick ties to tighten it horizontally and I tied some cables together to keep them a bit more away from the plug.  If it cut out, I could give it a little wiggle and it was ok again.  Well now, wiggle does nothing.
Another point maybe to add that seems to be making more sense now - my instrument lights were "burnt out".  Not the indicators, but the lights behind the speedo/tach.  I took the bulbs out to change and what do ya know - no current coming to the bulbs!  Went back into the headlight jumble, but had left it for the moment.  Wanted to ride.  Now I'm thinking it's another indicator of the switch because I'm getting no voltage output at the brown wires either.

[sparker]

The connection is like this: 

[scottly]

That switch is completely different from the earlier one. If you check for continuity directly at the switch terminals for the red and black wires does it still check bad? The brown wires are for the taillight: when in the first switch position, the two brown wires are connected to each other, and one gets it's power via the taillight fuse and the black wire. With the switch in the second "park" position, the taillight brown wire is connected directly to the red wire, and there is no connection to the other brown or the black wire.

[bryanj]

BE CAREFULL there are 2 different switch bottoms that whilst both fit dont interchange electrically.
One switch bottom has one more spade connector, cant remember where its 4 or 5 maybe 5 or 6 spades.

There used to be a down loadable Emgo catalogue and yes the relay is still a good idea.

[bryanj]

A long time ago i downloaded the emgo catalogue but its huge, luckily i screenshot the switch page and here it is

[bryanj]

Bored so another screenshot

[sparker]

That switch is completely different from the earlier one. If you check for continuity directly at the switch terminals for the red and black wires does it still check bad? The brown wires are for the taillight: when in the first switch position, the two brown wires are connected to each other, and one gets it's power via the taillight fuse and the black wire. With the switch in the second "park" position, the taillight brown wire is connected directly to the red wire, and there is no connection to the other brown or the black wire.

Yeah - mine is the five pin connector.  If I do a continuity test on the male connectors with the plug unattached, with the key in the first position - on, (there is no park position on my bike) then I have no continuity between the red and black male connectors, which seems to me it should have because turning the key to on, would open the circuit to provide electricity to the other components.

[sparker]

Bored so another screenshot

That's the one.  I was looking at a Canadian site - Vintage CB750 - it's the five pin connector - I can get the whole switch or just the bottom component with the pins.

[sparker]

https://vintagecb750.com/products/switch-repair-kit

[scottly]

Have you removed the switch from the bike yet? For $12 Canadian the repair kit is worth a shot.

[sparker]

If I don't do it in the next couple nights, I'll do it over the weekend - see how it comes off.  If the bottom section does it, do I have to look at a relay?  I understand that the EMCO replacement isn't good for 15amps even though they say it works for the 750.  One member on here was selling the relays.

[scottly]

I believe the supposed Emgo switch problems were with the earlier 4 wire switches, which had wires soldered onto the back side with a plug on the end of the wires, as I recall a case of the soldered joint failing. If the problem is with the switch itself, and not the connection between the switch and the harness plug, I would try the kit.

[bryanj]

The Emgo bases used to be notorious for falling off the main body so its advisable to use extra retention as in zip ties or even gaffa tape

[HondaMan]

I believe the supposed Emgo switch problems were with the earlier 4 wire switches, which had wires soldered onto the back side with a plug on the end of the wires, as I recall a case of the soldered joint failing. If the problem is with the switch itself, and not the connection between the switch and the harness plug, I would try the kit.

This is what I've experienced, too. The type of keyswitches that are up in the instruments don't have the problems of the under-tank style earlier switches. I've experienced the Black wire desoldering itself from the switch because the switch is actually for the CB/CL350 bikes, same style but only 8 Amp contacts inside, so they overheat. After I repaired that switch I used it in a CB350 and it is still fine. They just look the same from the outside, except the CB750 version of that earlier switch has heavier wires (17 ga. if directly 'converted' to ASME/NEC standards).

[sparker]

I believe the supposed Emgo switch problems were with the earlier 4 wire switches, which had wires soldered onto the back side with a plug on the end of the wires, as I recall a case of the soldered joint failing. If the problem is with the switch itself, and not the connection between the switch and the harness plug, I would try the kit.

This is what I've experienced, too. The type of keyswitches that are up in the instruments don't have the problems of the under-tank style earlier switches. I've experienced the Black wire desoldering itself from the switch because the switch is actually for the CB/CL350 bikes, same style but only 8 Amp contacts inside, so they overheat. After I repaired that switch I used it in a CB350 and it is still fine. They just look the same from the outside, except the CB750 version of that earlier switch has heavier wires (17 ga. if directly 'converted' to ASME/NEC standards).

So, what I'm understanding is that the new replacement switches, the ones that sit under the instruments shouldn't pose a problem if I had to either switch the whole thing out or just the bottom white plastic part.  Right?  (I remember is was you HondaMan talking about the relay - so I'm understanding that for the 1977 750, it might not be necessary?)
I'm going to see if I can take the bottom section off the switch to see if I see a noticeable problem.  From there, I can decide if I change just the bottom part or change the whole thing?  Would there be any problem in the key section?  (Sorry, questions keep popping up!  But I'm really appreciating the feedback - it's helping a lot!)

[sparker]

Just found this great video that could be useful for others as well!

[sparker]

Ready to open it up tomorrow and check it out.

[bryanj]

Nothing to open up, just the contact part at bottom comes off the key part stays in one piece

[scottly]

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.

[sparker]

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.

Yeah - that's what I was thinking.  It confirms that the "key part" is really not the issue.

[sparker]

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.

[rotortiller]

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.

[sparker]

Took it apart & the new part is ordered! 

[HondaMan]

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.

[Don R]

https://www.ebay.com/itm/171399797755?fits=Year%3A1977%7CModel%3ACB750F&_skw=1977+CB750F+ignition+switch+parts&epid=171198409&itmmeta=01K3Y63CZ0APXAXGSXZZRYXP4G&hash=item27e8395bfb:g:TrUAAOSwbqpnP34q&itmprp=enc%3AAQAKAAABAFkggFvd1GGDu0w3yXCmi1ebgGzFxGMtYYVseHS8Nl1Gw0mLkRaxiSlClz3ipSkT8WBRr3%2B2dFYujhy%2FPuIdJul0sIy4wxk%2BhkyfHz1vq3t9hex8zQPMwQAZ5TfWxOQmA2%2BKoYtdEVLwcg0rZpSAirMyCWaVnsRV60FcDmmC4KfVTSQY%2FFUZCXEPLlIFBnnKm1Xr1VevYLZS8pQYkFl7p9hpQlsASk%2B7Mnh%2BpRz5wh3vGZZGuCZIHoC%2FJJ5Uyl96kI%2FNw1QCmBu%2FqyrO72MTbfvI8y%2B7A%2FvDXuSLH0oRuX4Oua9bytLNVU7FcCl%2Fud%2B2bLnhjmbp3nUL%2BbET%2B9TWJu4%3D%7Ctkp%3ABk9SR-7PjcafZg&pfm=0

[sparker]

Just got mine in tonight!  Too beat to go out to the garage, but will be in in the next couple days.

[sparker]

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.

[sparker]

Well, got the switch up and going - took it for a spin tonight and everything was good - thanks everyone!

[newday777]

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.....

[bryanj]

Can i guess that the rotating bit was 180 deg out when you fitted the switch part