Topic: New Project! 1970 CB750K1!

[Kevin D]

I’ll second what John says, when I got mine out of storage, I got it running and rideable before I spent for the repaint three years in. My helmet and jacket cost more than what I had in the bike: battery + tires. Fresh gas in the carbs and a new battery got mine started after a 15 yr park.

Here are the (re)painted parts on an 11/70 K1.
Accordion fork gaiters were standard.
There ought to be a witness mark on the frame tube where the ignition switch clamp was.
Your oil tank has a rounded cover, also not k0.
Gauges and seat were K1 only making them harder to get.
Don’t think I have seen a 7/70 K1 here. Nice!

[newday777]

Get rid of those carbs and find the right set. Those others will just make you nuts and waste your time. I always start my projects this way;

1. Get the ownership in your name, free and clear, otherwise you might be working on someone else’s bike. This comes from a bad experience. Don’t ask.

2. New points, plugs, set the valve clearances, ignition timing, check for oil pressure, and get it running. You need a key switch and the EMGO ones are cheap.

3. Sync the carbs and get it running really well. Costs nothing and you have to do it anyways. Use a clean, remote fuel tank. The original is full of crap. Don’t get distracted.

4. If it idles well, clutch and gearbox work fine and it has 5 speeds, start looking at what else it needs.

5 At this point, you will have spent $100 and have a bike that is worth 4 X what you paid for it. If you’re smart, you will sell it at this absolute “profit zenith”. If you are dumb like me, you will get into it. Now you can spend some real money (and say goodbye to it)……

Ha - unfortunately to #1, the owner still has to 'find' the title. I told him I'd pay him more if he finds it and he "swears he has it" - but I live in a place where I can get it titled as an "antique" - its a bit more of a PIA but if I have to - then I have to. I did get a bill of sale though - so with the title thing, it was either "keep waiting" or "finally get a CB750" again. You mentioned "dumb like me" - so I'm probably already apart of that club! 

I don't think I'm going to find a full set of carbs for less than $100 though to make point 5 correct!

As to the carbs, your K1 needs the 2 cable push pull roundtops not the 4into1 cable of the K0, so they will be cheaper to get. I bought a set in September at a local Japanese bike swap meet, Riceorama, for $30 so they are out there.

[newday777]

And you already have the 2 throttle cables on the bike. Leave the bars on it until you get it running properly.

[newday777]

Pm sent of possible carb set

[God of Thunder]

Thanks for the PM!

This is probably considered taboo - and I think they said "don't do it" with my K2 - but once I have a key switch, and I test on spark - is there anything 'bad' that could happen by dropping some gas straight into the cylinders and see if it fires for a brief second?

[newday777]

I've done it with a short spray of carb cleaner to get it to fire off.
Edit....starting fluid

[God of Thunder]

I've done it with a short spray of carb cleaner to get it to fire off.
Edit....starting fluid

Then I guess it's time to order a key switch! On this photo - it looks like a key would plug into the left molex connector - does anyone know what the two wires on the right would be for?



Also - any suggestions on where to order a key from? I've got this bracket on the handlebars under the tach, but if I recall, wasn't it mounted under the gas tank?

[newday777]

The 2 wires should be the horn.
Yes the key switch was originally under the tank but the bar mount was a popular accessory change. You can change that later.

[Kevin D]

A K1 has a round plug ignition switch and harness.
Your rectangular plug is a mod, and also the keyless mod.
Check later models to match that rectangular plug

[God of Thunder]

A K1 has a round plug ignition switch and harness.
Your rectangular plug is a mod, and also the keyless mod.
Check later models to match that rectangular plug

This is good to know - I haven't had a great chance to give the bike a 100% look over yet, but I did notice some suspect lookign wires near the main components near the battery compartment - I wonder if that's part of it. At first glance, it looks like this key might work. I'll have to see if I can find the correct wiring.

https://www.ebay.com/itm/386129929245?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20200818143230%26meid%3D53b5deaee4cc4c2bb1a7374bc9aeced9%26pid%3D101224%26rk%3D2%26rkt%3D5%26sd%3D125802832749%26itm%3D386129929245%26pmt%3D1%26noa%3D1%26pg%3D4429486%26algv%3DDefaultOrganicWebV9BertRefreshRanker%26brand%3DEmgo&_trksid=p4429486.c101224.m-1

[BenelliSEI]

I wonder if the other end of that plug lead has been spliced into your original harness? The original would have looked like this….

[God of Thunder]

I wonder if the other end of that plug lead has been spliced into your original harness? The original would have looked like this….

Unfortunately we got like 10" of snow today - so I can't get over to the bike to take a look! But I'm dying to know. I 'almost' took photos of that area, but decided I'd wait!

[willbird]

The 2 wires should be the horn.
Yes the key switch was originally under the tank but the bar mount was a popular accessory change. You can change that later.

It seemed to be a great way to ruin your OEM ignition switch if the bike was parked outside and got rained on.

Bill

[newday777]

The 2 wires should be the horn.
Yes the key switch was originally under the tank but the bar mount was a popular accessory change. You can change that later.

It seemed to be a great way to ruin your OEM ignition switch if the bike was parked outside and got rained on.

Bill

Some came with a flip lid that closed over and covered the top of the switch and nut to keep water out, though some were sold without.

[willbird]

The 2 wires should be the horn.
Yes the key switch was originally under the tank but the bar mount was a popular accessory change. You can change that later.

It seemed to be a great way to ruin your OEM ignition switch if the bike was parked outside and got rained on.

Bill

Some came with a flip lid that closed over and covered the top of the switch and nut to keep water out, though some were sold without.

My dad installed a couple "without" on his/my CB750K2 and a CL175 and both ignition switches went over the rainbow bridge :-).

Bill

[God of Thunder]

So today - I braved more snow and ice to head over to do a little digging into it..... why? Because the EMGO key came in. There is definitely some hacked wiring that I found - and I should have taken some photos of the wiring so you all could see how bad they look, but I forgot. I won't really dig into the motorcycle until the spring because right now it's soooo cold that its not much fun to get out.

With that said, I hooked up the new key and I have lights! 3 position switches, lights and starter work - I checked for spark by grounding the plug to the case on Cylinder 1 - and I have NO spark. So obviously that could be a number of things from coils (which I think ground to the frame and are currently not grounded), to the lose yellow wire I saw.

The main thing I wanted to point out here though, was while i was digging around, I noticed a 'chip' on the headlight bucket - and low and behold, I think we have a new color......I assumed it woudl have likely been red given the gas tank, but I think we've got a new one!



I think its VALLEY GREEN!

Additionally - I never noticed it before but on the underside of the tank, I think I see green overspray!

So I was planning on going red, but I think now - we'll go Valley Green!

[God of Thunder]

Also - as a side note, I am 'debating' putting in a new harness since this one appears to have had some modifications. I see vintagecb750.com has one, does anyone know the quality of their harnesses? Or should I try and repair the original?

[BenelliSEI]

I’ve used two or three on different years. Colour of some wires varies slightly, but no product issues. Make sure you order the right one for your year. There are slight variations.

[God of Thunder]

Small update - pulled the bike to the garage today to do some looking at it. I took a few videos to try and figure out the spark issue - but dang this harness is just.....just a job for sure.

I took a few videos and if you get time, I'd love your opinion on whether or not I should just put in a new harness - and I'm still leaning towards yes.

[BenelliSEI]

A new  K1 harness from vintagecb750.com is about $60. The small feeder harness from the alternator (the crumbled connector) is about $12. If you plan on doing a good job, get rid of that mess someone else created. Who knows what else is in there you haven’t seen yet. Print off a good colour copy of the wiring diagram for your bike. It’s not that hard and worth it.

[God of Thunder]

A new  K1 harness from vintagecb750.com is about $60. The small feeder harness from the alternator (the crumbled connector) is about $12. If you plan on doing a good job, get rid of that mess someone else created. Who knows what else is in there you haven’t seen yet. Print off a good colour copy of the wiring diagram for your bike. It’s not that hard and worth it.

I agree 100% - I can't imagine not doing it with as bad as it looks....I assume I can post outside links here, so I think this is about what I'd need?

https://4into1.com/ignition-switch-round-plug-honda-ca-cb-cl175-cb-cl-sl350-cb-cl450-cb750/

https://4into1.com/main-wiring-harness-32100-300-050-honda-cb750k-1969-1971/

https://4into1.com/alternator-wire-harness-31110-300-154-cb750-1969-1978/

And I think that yellow and red mess near the battey is one of these....

https://4into1.com/regulator-rectifier-lithium-lead-acid-honda-cb350f-cb400f-cb500-cb550-cb750/

[newday777]

I have a NOS Honda supplied ignition switch that should be a bit better than that 4into1 ignition switch. You can have it for $40 shipping included.

[God of Thunder]

I have a NOS Honda supplied ignition switch that should be a bit better than that 4into1 ignition switch. You can have it for $40 shipping included.

Sold! I'll send you a PM right now!

[newday777]

I have a fuse panel too for the K0/K1
$20

[God of Thunder]

I have a fuse panel too for the K0/K1
$20

You know better than me - if I need it, let's add it in there!