Author Topic: Relay "KIT" for helping the keyswitch, CB750 first...  (Read 1434 times)

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Offline HondaMan

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Relay "KIT" for helping the keyswitch, CB750 first...
« on: October 05, 2009, 08:35:09 AM »
OK, I'm getting ready to order the parts for these kits.
This will be a relay that lives under the seat, with the rest of the electrics, and a handful of little pre-crimped jumper pieces that you can origami together on a cold winter afternoon, then mount in your CB750. The object here is to bypass the heavy electrical loads on the aftermarket keyswitches we're all suffering from, which only have 8 amp contacts in them (and 20 AWG feed wires). These light-duty switches are intended to run CB200 and CB350 Hondas, but someone is adding CB750 connectors to them and selling them to fit these bikes, with short-lived results.

This "kit" will install something like the picture below, in its extravagant form. That form included me running a whole extra wire (the ORANGE one) to the headlight to remove most of the load from the electrical harness. I did this to see how much difference it made between using just the bike's wires and using the extra wire: the difference was about 0.25 volt improvement up front, which made a brighter headlight and hotter spark at the coils. Later, I added another GREEN wire between the headlight and the underseat ground, and was rewarded with a total 0.45 volt improvement up front!

I'll post a price for the kit after I get all the parts on the bench: it should be less than $25. I'm buying 100 each of the various connectors, 20 relays, and 50 feet of the various wire colors, to make 20 kits.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline andy750

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Re: Relay "KIT" for helping the keyswitch, CB750 first...
« Reply #1 on: October 05, 2009, 09:33:49 AM »
Is this for the pre-73 CB750s (one-fuse) or later? I am interested in a "kit" for my 72 750.

cheers
Andy
Current bikes
1. CB750K4: Long distance bike, 17 countries and counting...2001 - Trans-USA-Mexico, 2003 - European Tour, 2004 - SOHC Easy Rider Trip , 2008 - Adirondack Tour 2-up , 2013 - Tail of the Dragon Tour , 2017: 836 kit install and bottom end rebuild. And rebirth: http://forums.sohc4.net/index.php/topic,173213.msg2029836.html#msg2029836
2. CB750/810cc K2  - road racer with JMR worked head 71 hp
3. Yamaha Tenere T700 2022

Where did you go on your bike today? - http://forums.sohc4.net/index.php?topic=45183.2350

Offline motorhead55

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Re: Relay "KIT" for helping the keyswitch, CB750 first...
« Reply #2 on: October 05, 2009, 09:40:12 AM »
I also used that style relay for the starter button circuit on my '76 550F. Worked well. No more "maybe" starts when hitting the starter button.
1976 Honda 550F bought new in 1978
2006 Yamaha TW200 TrailWay
1967 Triumph 200cc Tiger Cub
2007 Dodge 5.9 Cummins Diesel, 6spd. Stick, 4X4
1955 European Spec VW Bug, 1700cc engine, Porsche 356 "A" brakes
1939 Willys Pickup
2003 Kubota B7400

Offline Terry in Australia

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Re: Relay "KIT" for helping the keyswitch, CB750 first...
« Reply #3 on: October 05, 2009, 04:34:52 PM »
Put me down for one Mark, and also, can you do me a relay kit for a CB750 so I can fit a louder car horn? Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)

Offline HondaMan

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Re: Relay "KIT" for helping the keyswitch, CB750 first...
« Reply #4 on: October 05, 2009, 07:34:36 PM »
Is this for the pre-73 CB750s (one-fuse) or later? I am interested in a "kit" for my 72 750.

cheers
Andy

It will fit all of them, Andy.  :)

See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline HondaMan

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Re: Relay "KIT" for helping the keyswitch, CB750 first...
« Reply #5 on: October 05, 2009, 07:41:14 PM »
Put me down for one Mark, and also, can you do me a relay kit for a CB750 so I can fit a louder car horn? Cheers, Terry. ;D

I could send one down, Terry, but would the shipping be worth it?  :-\

Do you have local automotive shops that could supply the relay? Then I could just send you a schematic of it, maybe a picture or two? It's simple to do a horn relay on your K0-K2: you hook the "86" terminal to the bike's BLACK wire in the headlight, the horn button from the handlebar to the "85" terminal. Then you run a separate wire from the battery to a separate 10 amp fuse (you'll have to add one of those blade-style fuseholders for this fuse), then the fuse goes to this new relay in the headlight, to the "30" terminal. Finally, the hot wire for the horn goes to the relay's "87" terminal. The horn's frame (or its ground wire, if it has one) goes to the bike frame.
See SOHC4shop@gmail.com for info about the gadgets I make for these bikes.

The demons are repulsed when a man does good. Use that.
Blood is thicker than water, but motor oil is thicker yet...so, don't mess with my SOHC4, or I might have to hurt you.
Hondaman's creed: "Bikers are family. Treat them accordingly."

Link to Hondaman Ignition: http://forums.sohc4.net/index.php?topic=67543.0

Link to My CB750 Book: https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=my+cb750+book

Link to website: www.SOHC4shop.com

Offline Terry in Australia

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Re: Relay "KIT" for helping the keyswitch, CB750 first...
« Reply #6 on: October 06, 2009, 03:12:58 AM »
Hey thanks Mark, that's all I need to know, I salvaged a nice loud horn off a car that my son destroyed, but I had no idea how to make it work on my K1. Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

"Crazy is a very misunderstood term, it's a fine line that some of us can lean over and still keep our balance" (thanks RB550Four)