1981 CB750C Build

iGreek

Been Around the Block
Hey guys! Picked up this 1981 CB750C about a month ago with plans to do a Cafe-ish build. Little did I know that I picked the worst start for a Cafe bike, with it being a C. Nonetheless, it was in quite good condition, being pretty much all original with only 19,XXX miles on it and I picked it up for $850. Carbs were recently done and the previous owner rode it to work and back. It was a 2 owner bike. So, I have a good start. This is my first bike build. I've had two '82 CB650s, but never did much with them. I'm a car guy and that's what I normally build.

Started tearing into it, as seen below. It's just going to be a budget build, that I can cruise around on, to the gym and with my girlfriend on the back.

I spray painted and clear coated a bunch of stuff on it, cut down the stock seat foam and re-wrapped it, sprayed the frame, threw on some cafe handlebars, and a few other things here and there. Waiting on a bunch of parts (All new controls, gauges, lights, etc) to install in the mean time.

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Where it's currently sitting at:

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Feel free to throw me some comments/criticism. I'd like to know.
 
Simple and clean so far. I like it! your right about the 81's, but it makes for a challenge :)

Looking forward to what happens next.
 
DUDE! I knew from the posts of yours on all the DOHC's you must have one!
I have the sister to your bike. Let the nay-sayers have their way... a C model is a diamond in the rough... so much potential!
looking good so far, let me know if you need any help.
Have you checked the valve clearance? It's probably THE easiest bang for your buck. Depending on what shims you may need I might be able to help out... or give advise on where to get them.

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Hoosier Daddy said:
DUDE! I knew from the posts of yours on all the DOHC's you must have one!
I have the sister to your bike. Let the nay-sayers have their way... a C model is a diamond in the rough... so much potential!
looking good so far, let me know if you need any help.
Have you checked the valve clearance? It's probably THE easiest bang for your buck. Depending on what shims you may need I might be able to help out... or give advise on where to get them.

Haha, yep! Anything has potential, just got dig deeper into some.

Just went through your whole build thread and damn...that's a build. Would love to tear mine down eventually, but I just want to ride at this point, haha. Will do. I haven't yet, but I will while I'm waiting for parts to come. Only thing I can do on it right now.

2 quick questions. Did you keep the air assisted forks on there and if so, should I just keep mine the same for now? The forks hold air fine and don't leak.

Also, I saw in your thread that you used the Carb Rebuild kit below. Is it everything I need? I'm not looking to rebuild them now, as it runs well, but just for future reference.

http://randakks.com/collections/kits/products/randakks-own-dohc-four-master-carb-overhaul-kit
 
Yep I kept my air ride front forks for the same reason.. hold PSI just fine. so why not have the "tuneablity" of adjustable pressure.
Randakks kits are top notch stuff by far. You wont regret it when the time comes.
 
Didn't get to ride it today, as I was busy, but wish I did because it was high 60s. Now it's gonna rain all week...

I managed to get something done on it today. I removed the Spawn of Satan, A.K.A. Auto Fuel Shut Off Valve. I've seen so many people complaining about it, that I figured I might as well remove it.

It starts right up now and seems to run a tad bit smoother, but it could just be imagining something about it being smoother. Guess I'll be able to tell when I ride it. Also, found a perfect size vacuum cap for the nipple of the second carb.

Also, now I should turn my petcock to off when I turn the bike off right? From what I've read you could get some leaks if any of the float needle valves don't seal properly. I'll just get used to turning it to off just in case.

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All gone!

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Also, does anyone see a problem with my fuel line routing? It's hard to route it any other way. It doesn't have any kinks in it, so gravity and the pressure from the tank should be enough right?

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I ditched the S.O.S. as well, nice simple mod to eliminate the chance of it restricting or completely stopping fuel flow.
Yes, always close the petcock, for the reason you stated.
Your routing looks OK except I think you have the filter backwards, should be an arrow on it showing direction of flow. It will work either way but you want the contaminants caught outside the screen where they are easier to see. The way you have it your filter has less surface area and will always look "clear".
 
That is what I thought as well. Fuel filter is backwards for sure. Ohh and please grab some better hose clamps. Last thing you want is fuel everywhere because a zip tie failed.

Nice start on the bike. It will me interesting to see where you go from here.
 
Appreciate it guys! Don't know how I overlooked the fuel filter like that. Previous owner had it like that, so I just continued with it. Already have the hose clamps ready to go on. Was being lazy last night and just zip tied it to test it out. For the better, since I have to flip the filter now, haha.
 
iGreek said:
Appreciate it guys! Don't know how I overlooked the fuel filter like that. Previous owner had it like that, so I just continued with it. Already have the hose clamps ready to go on. Was being lazy last night and just zip tied it to test it out. For the better, since I have to flip the filter now, haha.

I assumed it was a new filter, if the PO put it on I do not recommend flipping it over. Any contaminants it has already captured would be flushed out of it and into your carbs... Best to replace it now.
 
Yep best off to buy a new filter and stick it on the right way round.
 
Hoosier Daddy said:
I assumed it was a new filter, if the PO put it on I do not recommend flipping it over. Any contaminants it has already captured would be flushed out of it and into your carbs... Best to replace it now.

Makes plenty of sense. Any that you would recommend or should I just go grab one from a local hardware store? What are you running on yours? How many microns?
 
I use the same style that you have on there now, I will be using the same type on my GS as well. No idea how many microns they are but they work well for me.
 
Brodie said:
I use the same style that you have on there now, I will be using the same type on my GS as well. No idea how many microns they are but they work well for me.

Ditto, same as yours... I got mine from the small engine section at the local auto-parts store.
 
I have a set of 900c Cams you can slap in that bitch for a little extra power. Not a real indepth process either.
 
gijoe13844 said:
I have a set of 900c Cams you can slap in that bitch for a little extra power. Not a real indepth process either.

Haha, I know. I've looked at it before. Not really at that point in my build, but hit me up with how much you want for them.
 
Hey guys. Haven't updated this in a while, because the bike is on hold, until I come back from some vacation I'm having on the first week of April. Have bought a bunch of parts and will more coming in after that.

I do have a question though.

Problem I have now is that I removed the headlight bucket to paint it and as I was going to put it back on, I couldn't figure out where 4 wires go. Checked wiring diagrams, made sure everything was connected (they are, turn signals too) but nothing. Everything seems to work on the bike, so I'm a bit confused.

In the first picture, in the foreground, the green wire is the headlight ground, so that is it out. But what are the four in the background? Colors are 1 brown, 1 black and 2 green. Green and black are dual connectors and brown is a single.

Do these actually go anywhere or were they disconnected from the beginning? Any info would help. Thanks.

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I kind of remembered having the same puzzel on mine so I checked the schematic... You are getting close, looks like one of the green should ground the headlight bucket and the others are not used.
 

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Hoosier Daddy said:
I kind of remembered having the same puzzel on mine so I checked the schematic... You are getting close, looks like one of the green should ground the headlight bucket and the others are not used.

Yep! I actually found this same diagram here: http://www.cb750c.com/publicdocs/CB750K_wir_diag/Wiring_Diagram_CB750C_81_82.pdf

The one I was looking at was crap, so it didn't make it obvious but this one does. Appreciate the help!
 
Glad to help.... that's what it's all about around here. ;)
Is that arrigant fuck of a Canadian Admin "holysmokes"still being a God Damn DICK there? He is the main reason I quit posting and resorted to only searching their resources.
 
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