Author Topic: Noob - Just bought a 72' CB 750 - Did I make out or fail? (Read 9548 times)

Ericcb750 · « **Reply #25 on:** December 24, 2015, 08:56:34 AM »

That's awesome for $500 buddy!!! Wish I found one of those too!! I have the Haynes one and the Clymer one. I know it seems stupid but each one is good for different info..... so you've heard right, it does help to have the different ones. Let me know if you have any questions as I was a Noob not too long ago either buddy. Best of luck, these are awesome bikes...you're going to love it.

mrbreeze · « **Reply #26 on:** December 24, 2015, 09:46:07 AM »

I don't know what we have here for manuals. I bought mine on ebay years ago and it is copied. I had to get my own binder for it. Things changed through the years so you will want one that covers your year at least. Most of it will be about the same but through the years there will be differences in wiring diagrams and carb specs. I don't have Honda man's book yet but have only heard great things about it. As time passes you can build yourself a small library of info & history on these bikes. There are other sources besides here that tell you of changes in models through the years, how to read engine & frame numbers, paint colors.....all kinds of stuff. I have a Clymer book but have found mistakes and missing info through out it. I always say...you can't have too much info. If you have a Clymer and a shop manual and find conflicting info on something....you can usually sort it out by starting a post here.

edwardmorris · « **Reply #27 on:** December 24, 2015, 10:00:09 AM »

Welcome! Congratulations, quite the deal on the K2. Mind sharing the VIN (just the first few is enough)? Just want to see if its the early K2 or the late one. I love the early K2s for their uniqueness, and I believe there are more sandcasts than the odd early K2s out there. I'm surprised no one has mentioned Hondaman's CB750 bible yet, its an essential read for a 750 owner IMO. For your immediate issue, here is a wiring diagram for the K2, should help you track down the spark issue.

Restoration Fan · « **Reply #28 on:** December 25, 2015, 05:37:28 AM »

1. Congrats on a great buy and welcome to the forum.
2. Start a build thread in Projects. We love to follow along and it will prove invaluable to you for advice and as a way to document your project. You'll be surprised how many times you'll refer back to it to answer a question you have about what was going on several months ago and why you did what you did.
3. You can download the service manual and parts list from here on the site for free.
http://manuals.sohc4.net/cb750k/
4. Print out the service manual and put it in a binder. Keep it close by...you'll use it...a LOT.
5. Print out the parts lists and diagrams and put them in a binder. Keep it close by..you'll use it...a LOT. (This one surprised me how much we used it. It's invaluable because the drawings show how things should go back together and it gives you part numbers you can use for sourcing parts when needed. It will also show you parts that should be there for times when you'll go..."Hold on, I don't have one of those. Should I?")
6. Pictures, pictures and more pictures. Take them of everything. If you think one photo is good enough for something, take 5 instead. Take from every different angle you can imagine. Storage on external drives, SD cards or PhotoBucket is cheap. Having that photo that shows how things should go back together properly can be priceless.
7. Don't be afraid to ask questions. If you look back at the build thread in my signature (Senior project one), you'll see just how stupid some of the questions I asked are. But the guys on this forum will gladly answer the questions and, in most cases, won't even point out how stupid the question was. I live on the interwebs because I write programs/apps/web sites for a living, but I have yet to come across another forum that comes close to matching the helpfulness, generosity and brotherhood of this site.

Good luck.

Ron

WhizWit81 · « **Reply #29 on:** December 25, 2015, 12:39:03 PM »

Thanks Ed and I appreciate sharing the schematic - Electrical is what scares me the most so that's what I'm going after first. Only one way to learn..

- I've seen Hondaman mentioned and it seems the going theme is to just start collecting manuals and create a library, so that's my plan.

- As far as the VIN, the frame show's 20055** (not sure what, if any, hazards of posting a VIN are so..). The bike was actually titled as a 73' when we went to switch it over. My buddy mentioned the frame showed 11/71' on it. My engine VIN starts with 20133**. Does that mean that my engine is not from the original bike being the frame starts with 200 as opposed to 201 or does that have nothing to do with it? Should they match?

mrbreeze · « **Reply #30 on:** December 25, 2015, 01:42:00 PM »

No they don't match but should be reasonably close. The bike itself goes off of the frame #. An 11-71 would be a 72....don't know where they come up with 73. I don't have the info handy on the VIN id's but it's here somewhere. I know for fact that Hondachoppers site has it.

Restoration Fan · « **Reply #31 on:** December 25, 2015, 03:48:04 PM »

To expand on what mrbreeze said, the engine and frames were made at separate plants. When the 2 were married, it is usual that the engine VIN doesn't match the frame VIN on these bikes. In fact, it would be unusual if they did match.

As mrbreeze said, the #'s will usually be close if the original engine is still in the bike though.

Justin · « **Reply #32 on:** December 25, 2015, 05:51:21 PM »

G'day and welcome Rob, Merry Christmas.

Don't worry about the green wire, currently it isn't plugged into anything

and that wiring mess you posted doesn't look bad at all. Good find for $500.

I don't worry too much about the dangers of posting full VINs, folks around here are all curious when someone new joins the forum and we get to see another SOHC/4 resurrected. The VIN date has a lot to do with values and there are a lot of us who value the early 750s. I have a 1970 (also known as K0) and a 1971 (K1)

Sent from my iPhone using Tapatalk

edwardmorris · « **Reply #33 on:** December 25, 2015, 06:12:43 PM »

Quote from: WhizWit81 on December 25, 2015, 12:39:03 PM

Thanks Ed and I appreciate sharing the schematic - Electrical is what scares me the most so that's what I'm going after first. Only one way to learn..

- I've seen Hondaman mentioned and it seems the going theme is to just start collecting manuals and create a library, so that's my plan.

- As far as the VIN, the frame show's 20055** (not sure what, if any, hazards of posting a VIN are so..). The bike was actually titled as a 73' when we went to switch it over. My buddy mentioned the frame showed 11/71' on it. My engine VIN starts with 20133**. Does that mean that my engine is not from the original bike being the frame starts with 200 as opposed to 201 or does that have nothing to do with it? Should they match?

That's a pretty early K2, so expect to see some odd things when you work on the engine. Mark's/Hondaman's book explains it in better detail, but some of the earliest K2s had left over K1 engines in them, so sometimes the parts fiche doesn't match up exactly. Not a big deal, but these nuances are what make the early K2s so special

Don't need a library, I only needed the factory manual, factory parts diagram manual and Mark's book to resurrect my K2. A project thread here will pretty much fill all that's in between.

MoMo · « **Reply #34 on:** December 25, 2015, 07:02:36 PM »

Here's all the numbering info for you http://www.motorera.com/honda/h0750/four.htm

mrbreeze · « **Reply #35 on:** December 25, 2015, 07:19:34 PM »

That's one that I've got stashed away somewhere. Is it on our site? If not it should be. I remember looking at that before for the paint color changes year to year.

MoMo · « **Reply #36 on:** December 25, 2015, 07:25:43 PM »

Quote from: mrbreeze on December 25, 2015, 07:19:34 PM

That's one that I've got stashed away somewhere. Is it on our site? If not it should be. I remember looking at that before for the paint color changes year to year.

not sure if the info is on this site, I have it bookmarked as I frequently use it...Larry

Dino · « **Reply #37 on:** December 26, 2015, 06:38:30 AM »

There are several manuals available and each one offers info that the others don't. I have the original Honda shop manual, the Clymer manual and the Haynes manual. I use all three.

ALWAYS check for spark FIRST!

Coils hardly ever go bad. Points will always wear out and need replacement as well as spark plugs. Speaking of spark plugs, the one you showed in that pic is not screwed into the head all the way! I see threads showing. Be careful when you replace them. They should spin in easily by hand. If it feels like it's binding up it could be cross threaded. If so it's not a deal breaker it just needs to be rethreaded properly. It can be tricky but it can be done.

Electrical stuff scares you. OK, nothing new there.

Most people are freaked out by electrical issues. All those wires going all over the place. How can you tell whats what? Simple. With a color coded wiring diagram and a basic understanding of electricity.

Here's my simple explanation of how electricity works. First you need a power source which in this case is a battery. It has two terminals, positive and negative. Simply explained, electricity flows from positive to negative. The negative side of the battery is connected to the frame. Everything else that is connected to the frame is also "grounded". So, the engine is also grounded and that's where your spark plugs gets it's connection to ground.
Here's a good analogy of how electricity works. Think of the positive as a large tank of water at the top of a hill. The pipes that come out of it are the wires. Gravity pulls the water down the hill into the valley or "ground". This is the negative. Along the way we can run the water through things and it's downward force will do work for us. Everything goes from positive to negative.

Now, without the connection to ground (negative) the flow just isn't there so no work can be done. A circuit needs to have both positive and negative to work. So, when something doesn't work, first make sure it has a positive supply and a negative ground. When troubleshooting always work from the component that isn't working upstream towards the battery. I hope this helps.

That said, congratulations on your new purchase and welcome to the forum. You might want to check out my YouTube channel for some help.

WhizWit81 · « **Reply #38 on:** December 26, 2015, 08:13:26 AM »

Dino - I must say this is a pretty ironic turn of events. I started researching these bikes a few years ago, but had a newborn, new house etc - not much time, let alone funds available and a willing wife (now a 4yr old and 10 mo. old...ugh). I'm pretty patient and have been waiting and waiting and waiting..for something good to come along - which I think I have found. But, I like to research everything before I make a financial commitment, but more importantly, to know what the hell I'm getting my self into, before I actually get there...

Moral of the story is that I started watching YOUR videos months ago and have not stopped sharing with friends. I'd get up in the morning before work and watch each of your video's on your 73' basket case and daydream about grabbing my own to toy around with and bring back to life. By the way, how is it coming along?

I must say I'm honored and appreciate your input. You too Hondaman - I heard about your knowledgeable book from Dino (He may need some kickbacks for his marketing as I will be purchasing;) I appreciate your willingness to help people you don't even know and that goes for all of you here that have already commented and welcomed me in, just because of the pure love of bikes...

As for the spark plugs, I had them out at the time and just halfway hand tightened the 4th to see what it looked like through the fins.

The diagram that Ednorris posted is a helpful start, but I wish there was a CB 750 wiring for Dummies in laymen's terms. I get the flow of electricity, but when we start talking about what is what in the 40 year old tangled mess, its hard to identify what is what for me. I guess I just need to dig into the manuals. That being said, any wiring video's in the future Dino? That would be a huuuuuuuge help.

Thanks again everyone!

madmtnmotors · « **Reply #39 on:** December 26, 2015, 08:40:11 AM »

Quote from: WhizWit81 on December 26, 2015, 08:13:26 AM

I wish there was a CB 750 wiring for Dummies in laymen's terms.

Doesn't get much simpler than this:

http://oldmanhonda.com/MC/wiring750K1.html

You can even show/hide the different circuits.

Dino · « **Reply #40 on:** December 26, 2015, 12:35:24 PM »

Quote from: WhizWit81 on December 26, 2015, 08:13:26 AM

... That being said, any wiring video's in the future Dino? That would be a huuuuuuuge help.

Thanks again everyone!

Yes! I'll be getting to that a few videos down the line. I've been back at it since three weeks ago and it's going well!

Glad you enjoy the videos. Thanks for watching!

irish44395 · « **Reply #41 on:** December 26, 2015, 03:50:45 PM »

Quote from: Dino on December 26, 2015, 12:35:24 PM

Quote from: WhizWit81 on December 26, 2015, 08:13:26 AM
... That being said, any wiring video's in the future Dino? That would be a huuuuuuuge help.

Thanks again everyone!

Yes! I'll be getting to that a few videos down the line. I've been back at it since three weeks ago and it's going well!

Glad you enjoy the videos. Thanks for watching!
I am new to all this and I am enjoying your video's also
Pete

WhizWit81 · « **Reply #42 on:** December 26, 2015, 07:17:59 PM »

Thank Madmtnmotors - that definitely helps!

scottly · « **Reply #43 on:** December 26, 2015, 08:13:58 PM »

Did anyone else notice the visible threads below the body of the spark plug? It looks like it's not screwed all the way in. Hopefully it isn't cross-threaded....

mrbreeze · « **Reply #44 on:** December 26, 2015, 08:19:45 PM »

I think he mentioned earlier that he just turned it in by hand but hadn't seated yet Scott.

scottly · « **Reply #45 on:** December 26, 2015, 08:25:23 PM »

Thanks Fred; I did an Eveilan Woodhead sort of speed read through the thread and didn't see if it had been mentioned.

ogsmakdade · « **Reply #46 on:** December 26, 2015, 08:41:33 PM »

Welcome to the fold Rob

WhizWit81 · « **Reply #47 on:** December 27, 2015, 04:46:49 AM »

Hey Darryl - Thanks for helping me pick up the bike and randomly sending me pics of your bike - keeping my "bike itch" alive. Now lets get this thing running!

ogsmakdade · « **Reply #48 on:** December 27, 2015, 05:59:37 AM »

We will put in some work this week and see if we can get this pig to fire up!

Larry expect a phone call or three

MoMo · « **Reply #49 on:** December 27, 2015, 06:17:37 AM »

Quote from: ogsmakdade on December 27, 2015, 05:59:37 AM

We will put in some work this week and see if we can get this pig to fire up!

Larry expect a phone call or three

No problem, let me know how I can help if needed....Larry

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Author Topic: Noob - Just bought a 72' CB 750 - Did I make out or fail? (Read 9548 times)