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New to the cb750 what is what?

Haxxel

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Hi I just figured that what I realy want in my life is a bitchin looking café racer.

My approach to this is to start studying on the driver license test to be able to drive my bike when its done.
Second of all i decided that the bike I want is to be built out of a Honda cb750, so I sent my trusty friend out to help me by a cb750 (I work at a remote location at the moment so I could not do it my self).
With that done I now have a Honda cb750k 1981 and about $850 less on my account.
The thing has been standing around for something like 15 years and is a bit rusty and ugly. When hooked up to a battery the starter turns the motor but it does not start.

So my question number one is: What is the normal approach to get an old bike like this going? My plan is to by a kit and rebuild the carburetors, change all the oils, filters and spark plugs. Is there something more that is a must?

My second question is: What is what?! There seems to be about a million different cb750! My bike has so much different things than other cb750s i´ve seen, like the seat, tail light and so on. Is there some place where I can read up on all the different variations on this wonderfull bike?
Most important is what parts fits my bike? Is the frame different between my DOCH and a trusty old SOCH? Does wheels from a SOCH fit a DOCH? If i by a seat for a 1978, will that fit my 1981 and so on?

This is a huge question I know, but maybe you pros can point me in the right direction so I can start my life as a proud cb750 owner :D

Thanks to you all in advance!

// Axel from Sweden.
 
I bet there are several publications on the history of the CB750, maybe even some on-line. I am guessing that they may be more variations in Europe. I will let Stabler weigh in on this topic. He has been a great help and I'm pretty sure he is from Sweden.
 
Hi Axel.
Feels good to have another swedish cb750-(soon to be)-rider on this board!
My first suggestion would be; get a workshop manual for your model and year.
Then just get new plugs, make sure there is oil in it, clean out the carbs, get a fully loaded battery, some fresh new gas in the tank (if it's not all rotten with rust from sitting the las 15 yrs - then use a temporary tank of some sort) and try and fire it up. Chanses are it will!

If it doesn't fire up, let us know and we'll try and help out.

For the rest of your questions, what is interchangable between sohc and dohc, I'd say not much really.. But if you know your way around a grinder, ruler and a welder, anything will fit.

Var i Svergie bor du Axel?

Let us know when you've tried to fire it up.
 
A haynes manual is on its way.

The other components gives me some more headache, there are som many options!
Like pods, is some cheap pods from ebay a good idea?

Oil, spark plugs and filters must be possible to by in Sweden. Maybe some 10w-40 semi synthetic oil and a oilfilter from "Biltema" would do?
 
You can surely get filter and oil from Biltema. That's what I do. I wouldn't go with the 10w40 semi sythetic though. Wet clutch an additives in that oil don't play well and may cause your clutch to slip.
I do however know that Biltemas 20w50 mineral oil works perfect.
Regarding plugs, I'd go with NGKs instead of the generic ones at Biltema. But that's just because I've had a few plugs from Biltema crap out on me in less than 10 miles.
When it comes to pods, I would never run them on a 1979 and later CB750 due to tuning problems. I've never heard of anyone that have ever got those carbs to perform well with pods. They need the restricted air flow that the stock airbox causes, to perform as they should..
 
...
When it comes to pods, I would never run them on a 1979 and later CB750 due to tuning problems. I've never heard of anyone that have ever got those carbs to perform well with pods. They need the restricted air flow that the stock airbox causes, to perform as they should..

Excuse me for borrowing this thread, but being totally new on CB's, I need help to understand this "pod problem". I'm in the absolute beginning of the CB750 learning curve, and I look at a lot of bikes on internet and read as much as I can get my hands on. Also love this forum and all the knowledge found here. When looking at CB750 bike pictures I more than often find them being equipped with what I believe is carb pods (like in this video: http://youtu.be/CSd9xMAjgFQ?list=FLBgcdzQgLjQwEtywmnI0jIA ). Is the problem with pods just on post '78 models? Or am I totally missing something here (not even 100% sure what a pod IS... :/ ) ???
 
The pods (free flow open air filter) mess with how the CV carbs on 1979 and later years function. Due to the design of these carbs, a certain level of restriction in airflow is mandatory for them to function to specs. Or at least that's what I've gathered from my own research - someone else (DD) might have a better explenation..
The earlier years carbs don't operate on vaccum in the same way, thus can be jetted to work properly with pods.
 
Today Im going to biltema, and I will by the oil you recomend. My friend are goint to Autoexperten to by NGK sparks.
We have not yet found air filters in Sweden :/
I also going to by a battery at biltema, can i use the smallest i can find or will that spell trouble? I want to hide the battery later.

Now I have found this nice site and the carb rebuild kits looks nice. But they say it is for cb750f and not cb750k, whats the difference? I have figured that K is more "touring", C is more "costum" and f something else, "sport" maybe? What is the actual difference, what parts are not interchangable?
Edit: this is the site http://www.partsnmore.com/parts/honda/cb750

The pod question is very interesting, sooner or later I want to put some nice pods on my bike... This guy got it to work http://honda-cb750-s.456789.n3.nabble.com/I-GOT-PODS-TO-WORK-td4039223.html
 
Got it. Thx Stabler!

And if one should absolutely WANT pods, could you fit pre 79 carbs on a post 78 engine?
I think the spacing between the carbs will be an issue, but I'm not sure. If you're dead set on a post 1978 CB750 and are willing to change out the carb rack, I'd have to recommend the kz1000 smooth bores. They are a nice power upgrade as well. I'm still not sure about the spacing on the post 1978 intakes though. I need to do some more research on those.. Or maybe DD will straighten stuff out on this issue? :thumbsup:


Today Im going to biltema, and I will by the oil you recomend. My friend are goint to Autoexperten to by NGK sparks.
We have not yet found air filters in Sweden :/
I also going to by a battery at biltema, can i use the smallest i can find or will that spell trouble? I want to hide the battery later.

Now I have found this nice site and the carb rebuild kits looks nice. But they say it is for cb750f and not cb750k, whats the difference? I have figured that K is more "touring", C is more "costum" and f something else, "sport" maybe? What is the actual difference, what parts are not interchangable?
Edit: this is the site http://www.partsnmore.com/parts/honda/cb750

The pod question is very interesting, sooner or later I want to put some nice pods on my bike... This guy got it to work http://honda-cb750-s.456789.n3.nabble.com/I-GOT-PODS-TO-WORK-td4039223.html
What that guy did was covering his pods with tape to restrict airflow.. It will take some tinkering to get that right - and you will have to like the look of tape on your pods. And you still need to rejet and do plug chops to get it tuned right. But hey, that's your choice.
On the matter of difference between carbs, there's a LOT. Instead of trying and list everything here I will give you this link: http://www.partssweden.se/honda that shows where you can find exploded views of each style of carb and buy the needed parts here in Sweden (or just lift the OEM-numbers on the parts you need and go on Ebay-safari). Just punch in your year and model and you'll get your whole bike in exploded view with OEM-numbers on all parts. Priceless information when in search of parts on the interwebzzz.
Just make sure you have the right year and type of carbs on your bike before ordering anything. (For instance my motor CB750K5 from 1975 came with the 1978 PD-style carbs, because the PO had changed them out.)

I hope this helps out some.
 
And no, you can't go with the smallest battery you can find. You need a certain number of Ah to turn the starter long enough to get your motor to fire. If you're converting to battery-less, that's another question. There's some small super-cell batteries people use, but certainly not at Biltema. I've never done that on a post 1978 CB750. You'll have to ask someone else on that.
 
Alright! I have been making great progress. Me and my trusty friend have ripped down a good part of the bike just of curiosity and have learnt a lot. We disassembled the stuck breaks and massaged them into working order, changed the fuel line and filter, new battery, oil, oil-filter, got rid of some ugly bags and so on. I also took the carburettors home and ordered a rebuild-kit with o-rings and screws, kinda pricey tho :/ Anyhow, after some late nights and a lot of tinkering my carb bank was sparkly clean and with fresh rubber and screws.
The weekend came and I got to mount the carbs to the bike. After some fiddly work I got it in place, but the choke cable is sized shut, impossible to move, got to by a new one. The tank was not working right so a soda bottle got to be the gas tank for the first test.
After some work and fixes... VROOOM!!! It started! :D Victory!!!

The day after we assembled the rest of the bike and took it for a test drive. It starts with just the touch of the starter button, wonderfull. So it goes, and stops, and lights is working.

The motor starts willingly at the touch of the starter and goes until I ask it to stop. But it spews out smoke and smells bad, it also has a a little clattering sound to it, what can it be? I think it goes kinda rich, but Im worried that the piston rings is bad :/
I have not adjusted the carbs in any way, I just lined the valves by eye and the pilot screws is just screwed in place and then backed out three turns (one turned out further out then the others :/ ) maybe it need some adjusting, but I don´t know how.

Also the brakes work, but not good. The front brake is really hard to use and when applied with maximum force the breaking isn't that impressive at all.
The neutral light does not work, the lamp is fine so maybe the switch is bad.
The charging system is not working very well, at the end of the day the battery was low and I was unable to start the bike. I measured the battery to 12,3 and when I started the engine it went up only to 12,5 rising a tiny bit when reved. The coals was very uneven, one twice the length of the other, can that have anything to do with it?

So as you can tell, great progress with happy faces but also many new questions to you guys :) I will maybe start a build thread :D
 
What color smoke? From what pipe? How does it smell? Like gas?
Someone else have to fill in on the charging. I ride a sohc so they have different charging systems I believe..
 
The smoke is mostly white, but when i was driving behind my friend when he tried it I think I saw a hint of blue, but im not sure. My friend did not se any blue only black/grey. When reving the smoke gets darker.
 
Ok. Has it lost any power? Or does it still pull strong? Lost power could equal bad piston rings/bad compression. Just smoke and the same power could be a leaking valve guide.

You could also have a rich condition. Pull your plugs and let us know how they look. Clattering sound could be your carbs is out of synch.. How does the smoke smell? Like unburnt gas or like burnt oil? (Can you tell the difference?)
 
Heh, I don´t know if it has lost any power. This is the first time I have started it and the first time i have ride it.

However I rode it this weekend and it goes rich, it smells rich (yes I can tell the difference), the plugs indicates it as well (dry and black).
I need a new filter, but the carbs need some adjustments, how is this done? Do I need some equipment, can it be done by a shop or do I only need some instructions?
 
That depends on what needs to be done to your carbs. I do all my carb work myself with "ordinary" tools. You might need to get them carbs ultrasonic washed to be sure they're clean. And you will prolly need jets and to adjust your needles to lean it out. And a good vacuum synch. Depending on your mechanic skills, this should all be doable without letting a shop do it.
 
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