Topic: Spark at 1 & 2, not at 3 & 4. What??

[HondaMan]

Cliff: the K3 and later 750s have a START button that turns OFF the headlight when pressing for START. The housings on those switches distort if halogen headlights got installed, and the failure is on the "unpressed" side's contact for the headlight. Either the switch can be replaced, or the headlight can be powered by jumping into a BLACK wire to power the Hi-Lo switch on the left-side handlebar.

Or, I can make up a Start Button Saver relay kit for you, but postage would be nasty. I could send you a schematic if you want to make your own? It's just a relay.

[Magpie]

Thanks Hondaman!
The strangest thing happened when I connected a black wire to one of the blue wires, it seemed to reset the headlight system. I disconnected the black wire, hooked up the blues as they should be and the On/Off  switch works as does the Hi/Lo. Hit the starter button and the headlight goes out. It's a miracle!!
We'll see how long that lasts. I did spray some contact cleaner into the On/Off switch last night.
It is a Halogen headlight to.
Hondaman does it again.
Cheers,
Cliff.

[HondaMan]

If that headlight is more than 50 watts (many of them are 55/60W for this bike) then it will cook the switch again and make it act up all over.

Sort of like the neighbor's 2-year-old here....

[newday777]

Thanks Hondaman!
The strangest thing happened when I connected a black wire to one of the blue wires, it seemed to reset the headlight system. I disconnected the black wire, hooked up the blues as they should be and the On/Off  switch works as does the Hi/Lo. Hit the starter button and the headlight goes out. It's a miracle!!
We'll see how long that lasts. I did spray some contact cleaner into the On/Off switch last night.
It is a Halogen headlight to.
Hondaman does it again.
Cheers,
Cliff.

The contact cleaner did it's job. The switch was covered with black carbon from the arching of the high loads. Spraying in the contact cleaner and working the switch cleans off the carbon, temporarily, and as Mark says, the neighbors 2-year old will return again when you need the light.
Get Hondaman's switch saver relay he said that he would make up or make your own relay to take the load away from the headlight switch.  What the relay does is uses the high/low switch as a trigger of lower current 12v( so the switch doesn't burn) and the relay which is rated for higher amps and the bigger wire from the battery that you will add handles the load of the higher wattage headlight bulb, or you can also just change out the headlight bulb(H4?) to a LED bulb(draws lower amps so the switch doesn't burn).

[Magpie]

I changed out the Halogen headlight to a standard sealed beam.Hopefully that will help. I'll look for a LED unit.
Thanks for all your help!
Cliff.

[newday777]

I changed out the Halogen headlight to a standard sealed beam.Hopefully that will help. I'll look for a LED unit.
Thanks for all your help!
Cliff.

If you have a H4 headlight?.
Get this LED bulb from Electrical Connection it draws only 24 watts. You will be amazed at the output of these. And they last, I have their bulbs in my GL1800 for 10 years now.

https://electricalconnection.com/index.php/product/led-headlight-bulb-h4/

[HondaMan]

Thanks, Stu!
I do indeed have an a track record: I'll take yours! I didn't want one with a fan inside the Vetter, too much complexity for a headlight (IMHO). The other H4 LEDs I have seen locally have been uninspiring at best, mostly for lack of focus: they look like a shotgun pattern across the pavement.

Denver, CO is not known for stocking anything of special-purpose types: EVERYTHING here is always generic, and as cheap as possible (but not the price). That's why all day, 7 days a week, there are multiple Amazon, Fedex, UPS, DHL, and various specialty-delivery companies delivering 'stuff' everywhere in my neighborhoods. It's become amazing: we'll go out and walk the dogs for 1-2 hours and will see every brand of delivery company at least once, and usually twice in different vehicles, on a walk: I've seen up to 4 different Amazon trucks (one was electric! It got towed away about 2 months ago, though) in one walk. It's always the 'special' parts/things/widgets, too, that are coming when we talk with the neighbors: everyone here is frustrated with the lack of product selection (for ANYTHING) around here in the last 15+ years. I have been looking around here for just such an LED for more than that long, and not single vendor carries anything like it, but for the occasional Sylvania "replacement LED" headlights that can't make it half a block.

[PeWe]

I had to visit CMSNL to verify the headlight on my K6. It had done 2 seasons and +17.000km when I bought it. So not sure about stock light .
It had H4 when I bought the bike.
CMSNL show a H4 socket, 3 poles, HI, LO and ground
But a strange design of the bulb

https://www.cmsnl.com/honda-cb750k6-four-european-direct-sales_model14384/partslist/F01-1.html

The US version a sealed beam variant.

I did not have any issues with handle bar switches. Only the wirings when I replaced handle bar with wiring outside.
I did not grind deep enough in the switch housings so a wire could be squeezed and some shortages until I did it better

So my bike's switches survived until 96.000km when I restored the bike with new, not sun bleached switches.
Law here about LO during daylight. So constantly on.

It got relays, not only for less amps to the switches, better light and aftermarket ign switch that could have weak connectors.

[HondaMan]

It got relays, not only for less amps to the switches, better light and aftermarket ign switch that could have weak connectors.

Yeah, Per: those aftermarket switches got me in 2006 when the wires melted right off the back of the switch (Red and Black) on the way home from work one day! When I took it apart, and the old OEM switch (the key wouldn't stay in that one anymore, kept falling out) I found the contacts inside the OEM switch were more than 2x larger than in the new EMGO keyswitch. Then I noticed the wires inside its black sheath of the EMGO switch were only 20 AWG size (actually were slightly less than that) while the 750 switch had 14 AWG size (slightly thicker, a JIS size, probably). That's why they melted off: the 750 can pull up to 16 amps through that switch with the headlight on HIGH and the brakes on.

That's when I first made the Keyswitch Saver Relay kits, along with the new version of the Transistor Ignition.

[PeWe]

Mark, it was thanks to your posts about the weak ign switch I added relays. Headlight relays was part of it too.