Topic: Modified Starter Wiring '73 CB750

[Slopesideandstreet]

I'm new to this forum, so "be gentle".  Ha.

Anyways, I recently picked up a '73 CB750 that had previously been built out as cafe. Major mods were done well, but they really made a mess with wiring. I'm working on the starter circuit (didn't work before) and have replaced the solenoid and key switch.

Key Switch is now a 3 position with spring loaded momentary start, so I can bypass the questionably wired controls and starter safety (yes, I weighed the risks).

Here's my question:
Battery-Solenoid-Starter is simple and clear.
But the relay wires seem odd. Checking continuity and a quick test shows function with:

Black relay wire to key hot momentary.
Red/Yellow to ground.

Is that right?  Red/Yellow to ground? Just seems odd to me. Keep in mind I'm simplifying this circuit. Also, look at the attached schematic for a similar design, though it only shows 1 relay wire in and you need to pretend the starter button is in the ignition key switch.

Thanks for any guidance!

[Bodi]

First, the starter relay coil is not polarized, 12V on it regardless of which wire is positive will operate it just fine.'

Also:
- A 30A fuse is excessive. 30A will damage the wire gauge (between 18 andd 16ga) on an original harness (and even homebrew wiring is mostly 16ga or even 18ga wire) and the bike does not use that much power - the original main fuse was 15A. There is some sense in having a sub fuse (powered from the main fuse) for lighting, a failing headlight can cause a momentary hard short as the filament falls apart, blowing the fuse. Losing lighting at speed is not great, but losing ignition simultaneously could be a lot worse.
- The original starter button allowed both hands on the bars when starting, safer than one handed if the bike happens to be in gear (and you removed the safety circuit). I see you weighed the risks, but I would try to use the switchpod starter button. I have seen bikes with the automotive keyswitch though and they seemed fine, owners undamaged (although damaged owners might not be riding any more?).
- I recommend including a kill switch - the one on the switchpod is ideal but I don't know if you're using them. Strange things happen, and being able to cut ignition power without taking a hand off the bars is useful when the shinola hits the fan. The OEM one just cuts coil power, so you would still have lights if you needed to use it at night.

[Slopesideandstreet]

Thanks, Bodi!

The extra notes are great too.
- Fusing. The previous owner/shop really messed up the wiring, so I putting in a blade fuse block and creating sub-fuses for all major circuits. Main 15A, Headlight 7A, etc. The schematic I included is similar to what I am doing, but way too simple and missing some features I am putting on.
- Totally get it on the switch location. I may relocate it to the bar switchpod, after I get this girl back to life. I also am planning to install a neutral indicator for safety and confidence I am actually in neutral.
- I am installing a right hand kill switch at the throttle wired to the coils.

Thanks again.