Topic: 1970 CB750

[jbonham]

 So last year I received as a gift a 1970 CB750 (K0 or K1?)from my father-in-law. It was his which he purchased brand new but stopped riding it around 1981. It was kept in his garage but wasn't kept covered or clean by any stretch. There was a fire in the garage at one time and thankfully the only damage to the bike was the windshield and bar grips melted. I have done a frame off strip so that I could get the frame sanded and repainted along with some other misc. parts.

At this point I am rebuilding and have the engine back in the frame and am starting to put the carbs on. I marked all the appropriate parts so I would know where they go but I left something out. At the bottom of each carb bowl you have the nipples that go somewhere. I have the original Honda Shop manual and a new Clymer manual but neither of these tell me where the lines go. Also, in what order are the plug wires connected for this bike? I know one coil controls 1&4 and the other controls 2&3 but that's about it. Plus the manual says nothing about the removal and reconnection of plug wires. I find that sort of strange.

I am sure I sound like a total doofus for not paying attention but it was a year ago that I had it stripped so as far as remembering exactly where the lines go is a small mystery.
I am also wondering how hard it is to rebuild my wiring harness for the bike? I am afraid that after my father-in-law pulled the bike apart at one time he didn't get everything exactly right and that's why it never started again.

Any information you can give me about this would be appreciated.

Thanks

[cameron]

Bottom of carbs = overflow hoses?
They go to nowhere. to the air under your bike just in case you overflow.

[xenoscr]

The tubes are drain tubes they don't connect to anything they're routed so that they hang out over the swing arm.

The pistons are order 1-4 left to right as you face the same direction as the bike. So one coil powers the two outer most cylinders and the other powers the two center cylinders.

Partsnmore.com yamiya750e.com sells replacement wiring harnesses. I'm not sure I would redo the harness myself. More power to you if you do.

edited: partsnmore.com sells harnesses for newer models, yamiya750e.com sells the older style.

XeNoSCR

[dhall57]

Show us the pics - jbonham

[Johnie]

I highly doubt you need a new harness unless the mice got to it. All you need is the wiring diagram and a Honda service manual. All the wires are color coded so that is a huge help to you. I wonder if your father-in-law blew a fuse and did not know it. That is all it takes for the bike to be dead. Get a new battery so you have that department taken care of and move on from there. This will be a process of elimination and with the help of the guys here you have the problem 50% licked already.

[jbonham]

I would be happy to post pics although I am sure to take some ribbing from the guys here. This is a home project so cash is very low (I am unemployed and have health issues) and the bike doesn't look the way I have seen other bikes on the forum. It is dirty, grimy and in general disarray. The only reason the wiring might be an issue is because of the splicing that was done by the in-law. He is a great guy he just decided that some mini-ape hangers fit his style on this bike. I have the original bars now which were found buried in his garage. The decision on the bars led him to splice together wires and cut some of the bullet connector ends off of some of the wires.

All of this together creates a big problem for me since I am not electrically inclined and have very little experience with a multimeter. In the headlight bucket he used a terminal strip to connect wires and not being able to remove the headlight bucket unless these were removed I am now at a loss for how they are to be reconnected.

That is just a little history so far. If you still want pics I will post them. I have lots of pics of the strip down and am now taking pics of the process as it gets rebuilt. Like I said, it isn't pretty and shiny but if I can get it running it will give me years of joy I am sure.

[Johnie]

No need to apologize for your bike man. The majority of us found our bikes in that same condition. We know where you are coming from. The guys on this board are glad to see another 750 being saved from the junk yard. So send the pics. We will be kind believe me. Now, to the bars and wiring. If your father-in-law just cut off the bullet connectors and spliced wires on the end to extend them...no big deal. You can cut off the splices and put the bullets back on. They are available. Since it is all color coded you can then do the connections in the headlight. Glad to hear you took pics of the strip down as they will be very helpful when you put her back together.

[MCRider]

I think overflow is more technically correct than drains. If the float sticks and the bowl overfills fuel will come out there. You cannot actually drain the bowls from there. When you turn the drain screws, fuel comes out from behind the head of the screw, very low tech and messy.

Back to the overflows. The bike will run fine with no hoses on those tubes. One would hope they are never used. In stock trim there is one hose each and they are ganged together and slip down between the swingarm and the engine, low enough that the fuel will not touch anything except the ground. And the tire if you are moving. 

[jbonham]

It has been an experience I will never forget. Considering that I have never done any work on motorcycles I feel as though I am making progress for sure. As parts came off the bike I used a simple ziplock baggie system for nuts, bolts and other small misc parts and then labeled each one. Bigger parts were easier of course because who can forget what a fender looks like, right?. I went through and cleaned and rebuilt the carbs by replacing gaskets and needles if needed and cleaning any burned areas inside the bowls. The bike wasn't ridden all that much so most everything is in good shape except for being dirty.

There will be several parts that will need to be purchased like a new master cylinder, maybe some cables and a new headlight. I go through the father-in-laws garage every once in awhile to look for parts that I am missing like the light cluster that sits on top of the handle bars. Some parts I am sure I can get through people on the forum that sell extras and others parts I can get from an online store.

I will get some pictures up in a few days to every one can see the monster I am dealing with. I am very excited to have a group to talk with about it. While my wife loves bikes she just doesn't understand most of what I am talking about.

Feel free to post, email or pm me if you have questions or comments about the bike or what might be helpful in the rebuild.

jbonham

[754]

You need to know what you need..  no light cluster handlebar clamp on 70 or 71.
 Do you have big sidecover with louvers os small ones ?

 Plastic Guages or Steel ?

[WFO]

It has been an experience I will never forget. Considering that I have never done any work on motorcycles I feel as though I am making progress for sure. As parts came off the bike I used a simple ziplock baggie system for nuts, bolts and other small misc parts and then labeled each one. Bigger parts were easier of course because who can forget what a fender looks like, right?. I went through and cleaned and rebuilt the carbs by replacing gaskets and needles if needed and cleaning any burned areas inside the bowls. The bike wasn't ridden all that much so most everything is in good shape except for being dirty.

There will be several parts that will need to be purchased like a new master cylinder, maybe some cables and a new headlight. I go through the father-in-laws garage every once in awhile to look for parts that I am missing like the light cluster that sits on top of the handle bars. Some parts I am sure I can get through people on the forum that sell extras and others parts I can get from an online store.

I will get some pictures up in a few days to every one can see the monster I am dealing with. I am very excited to have a group to talk with about it. While my wife loves bikes she just doesn't understand most of what I am talking about.

Feel free to post, email or pm me if you have questions or comments about the bike or what might be helpful in the rebuild.

jbonham

Hint: Take lots pictures of the disassembly to help you put it back together.

[jbonham]

Really putting it back together isn't much of an issue other than it just takes time. I am familiar with the parts but sometimes cant remember where tubes or hoses go.

Lots of pics of the strip down plus labeling everything was a huge help in knowing which nuts and bolts go where. I honestly hadn't thought about using the before pics for the rebuild. A good thing to know while doing these things definitely. Just something I didn't think of since I haven't run into anything that I didn't know where to attach.

I have two smaller side covers. One that covers the oil reservoir on the right side and the other that covers the battery box and some of the electronics. No louvers

As far as the bars go, what is used to attach them to the forks? I have the piece that slides down over the tree and also holds the gauges but not sure how that is permanently attached.

I assume that there are bands that attach the gauges to this piece but those weren't with the bike. I believe the gauges are metal. Dark face gauges with white numbering, black outer with a chrome ring surrounding. I can post pics of gauges if needed.

Thanks,
Judd (jbonham)

[754]

K1 ises metal case guages, each have 2 indicator lights inside. 
2 chrome bands hold them to the top tree.

[WFO]

Really putting it back together isn't much of an issue other than it just takes time. I am familiar with the parts but sometimes cant remember where tubes or hoses go.

Lots of pics of the strip down plus labeling everything was a huge help in knowing which nuts and bolts go where. I honestly hadn't thought about using the before pics for the rebuild. A good thing to know while doing these things definitely. Just something I didn't think of since I haven't run into anything that I didn't know where to attach.

I have two smaller side covers. One that covers the oil reservoir on the right side and the other that covers the battery box and some of the electronics. No louvers

As far as the bars go, what is used to attach them to the forks? I have the piece that slides down over the tree and also holds the gauges but not sure how that is permanently attached.

I assume that there are bands that attach the gauges to this piece but those weren't with the bike. I believe the gauges are metal. Dark face gauges with white numbering, black outer with a chrome ring surrounding. I can post pics of gauges if needed.

Thanks,
Judd (jbonham)

Exactly my point and it really sucks when your looking at a part and have that ( how the hell did this go in there ) conundrum, which halts the assembley process or you find out later it's in wrong and you end up tearing it down again.

[jbonham]

Yep those are the gauges I have. Two indicator lights in each. So is there a good place to get the metal band that holds the gauges to the top tree? As far as the top tree goes, is the nut the only thing that holds the top tree on?

Is it just me or shouldn't the manuals have this stuff in there? I have the original and the clymer but nothing about assembly really.

Another issue I ran into is that the forks got damaged some how. Slight damage really but the right side stop that keeps the wheel from going completely sideways has been knocked off. May be a small thing but I could see how it could be dangerous if the wheel is forced all the way to left without something there to prevent it from a total 90 degree turn.

[Kevin D]

Slight damage really but the right side stop that keeps the wheel from going completely sideways has been knocked off. May be a small thing

Your fuel tank is at risk of being dented.

[jbonham]

I have definitely considered the damage that might occur to the tank because the stop isn't there but a bigger concern is a freak accident of the front wheel going 90 degrees on me and upending me on my head. My family would argue it probably wouldn't do much damage to my head but have concerns about the bike .

Tomorrow when I get time I will upload the photos I have. I have a lot of pictures so I will be a little choosy as to what gets posted. If there is something specific you want to see then let me know and I will try my best.

Judd

[754]

Yor top tree should have clamp bolts on outer ends..

 Do you carbs have orks on top , or cables ?

[traveler]

A couple of things I'd like to mention:

1. We are happy to have you....WELCOME to your second home!

2.  We are glad you are saving this K0 or K1 from extinction....I, if no one else, are willing to help you get the old girl back on the asphalt where she belongs!

3.  Believe it or not, once you REALLY start looking at ANY part of these bikes, it is really pretty straight forward....the Japanese engineers that designed these bikes really knew what they were doing!

Again, WELCOME...hope you stick around, and if you need any help, please ask!


If you can, PLEASE post some pictures!

~Joe

[jbonham]

The carbs have forks that slide under a nut that lifts as you adjust it then the cable of course that adjusts them up and down.

The top tree has the holes for the bolts but I thought maybe there was something else that would keep the top tree from sliding upward after repeated riding. I guess the bolts are the only thing that keeps the top tree secure. The band that attaches the gauges I will have to find somewhere. There are no clamps for the bars so I will need to find those as well. Those seem easy enough. From what I can tell they are single pieces that bolt on top of the bars.

Getting ready to upload some pics so you guys will be seeing her soon.

[754]

Bars are held on with 1/2 caps used on many models.

 MAKE SURE, I repeat MAKE SURE that when you clamp your forks on top tree, that you have the torque limiting washers, (They probably have a diferent name).. or you will snap the end off.. and them trees..no longer grow on trees..

 You can post a wanted ad in another section of the forum.. but PLEASE state your location.. sometimes parts can be close to you..

[Johnie]

Those carbs are from a K1 and up. Like in the pic below. The 2nd pic is of the KO carbs. I would watch for a lower tree on eBay or this board. You really want the fork stops on that tree or you will damage the tank. If you need pics of a certain area let us know. I have a bunch of pics of the KO and K1 if you need a look. Click the pic to enlarge it. You can download a service manual from this site. KO had plastic gauge cases and K1 had metal gauge cases. Sounds like you may have a K1 titled in 1970. If your side covers are solid then it is the K1 model. KO had the slots in the side covers sometimes called "shark gills." You pics will tell us a lot.

[Magpie]

Ditto on 754's comments! I've cranked those up tight and found a broken end the next morning.   Not a good feeling and the top trees are getting expensive! Don't forget the thicker washer in the split on them.  the washer will have to have a flat spot ground in it so the forks can pass through it.
Cliff.

[GammaFlat]

Ditto on 754's comments! I've cranked those up tight and found a broken end the next morning.   Not a good feeling and the top trees are getting expensive! Don't forget the thicker washer in the split on them.  the washer will have to have a flat spot ground in it so the forks can pass through it.
Cliff.

Magpie, 754...
what is the thickness of those washers?  I had it at one time and lost it.    I need to make up a set.  Thanks, John

[Magpie]

I read somewhere here that they are similar in thickness to the washers that go under the nuts that go onto the studs to connect the head to the cylinders. I have some to measure but they are buried under my workbench in storage. If I can get to them I'll do that later today.
Cliff.