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Carb Rebuild - 1981 CB750K

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Carb Rebuild - 1981 CB750K

Ccheese4
Hey all! I've been lurking about the forums for the past couple of days digging up info. My dad recently gave me his 1981 CB750K and I've been working on rebuilding it. The bike hasn't run in about 25 years.

I got to the carbs, which are incredibly clogged up with varnish. Seeing as this is my first rebuild, I'm kinda learning as I go. In the process of cleaning, I decided that I was going to remove the diaphragms so that the carb cleaner doesn't destroy them. So, I removed the back cap expecting to see a diaphragm... and there isn't one where I expected it. Is this the way it's supposed to look, or is the diaphragm completely missing?


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Re: Carb Rebuild - 1981 CB750K

Johnnylevi
That is what their supposed to look like. Is there a plastic sort of retainer underneath the slide? I think this link will help a bit! cant be sure its the one i used since the computer I'm on is a dinosaur, but give it a shot. http://www.cb750c.com/publicdocs/SeanG/Honda_Carb_Manual_revE.pdf
1981 SS with Kerker 4-1 exhaust and extremely attractive rider.
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Re: Carb Rebuild - 1981 CB750K

Ccheese4
Is the round metal surface that you see there the slide? Forgive me, I know little to nothing about this so far.
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Re: Carb Rebuild - 1981 CB750K

seestheday
yep, its the top of the vacuum slide.  It's more of a vacuum puck though.  CV carbs don't have slides like carbs that are operated by cables.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals

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My cb750 video site
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Re: Carb Rebuild - 1981 CB750K

SoonerRon
In reply to this post by Ccheese4
There is a really good carb manual at the cb750c.com web site by a guy named Sean that is awesome. It will tell you everything you need to know about cleaning the constant vacuum carbs on DOHC bikes.

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=13611

I recommed using pine sol to soak the carb bodies after you have them broken down. You'll be amazed at how well it works! 
1979 CB750K
1978 CB750 Four SS (gone but not forgotten!)
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Re: Carb Rebuild - 1981 CB750K

cdaiscool
If you use the Pinesol trick, I warn you that you need to be extra-vigilant about cleaning everything. Mine were oily, and oil + Pinesol = solidified gunk.

Took me quite a while to figure out that it'd gunked up my fuel passages and #4, as a result, was dry.
Turbos, Hondas, 4-bangers, what could go wrong?

Fuelly

Shiny: [...] Considering the weather you've had to put up with I'd say you get an Iron Butt award and a Frozen Nipple trophy to go along with it. First time I've ever posted the word nipple... it ends here.
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Re: Carb Rebuild - 1981 CB750K

cdaiscool
Other than that, if you need any help or anything with the carbs, feel free to shoot me an e-mail. I rebuilt mine this past Spring.

I've got the same bike, too.
Turbos, Hondas, 4-bangers, what could go wrong?

Fuelly

Shiny: [...] Considering the weather you've had to put up with I'd say you get an Iron Butt award and a Frozen Nipple trophy to go along with it. First time I've ever posted the word nipple... it ends here.
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Re: Carb Rebuild - 1981 CB750K

SoonerRon
In reply to this post by Ccheese4
yeah, for sure the pine sol is not for degreasing but for dissolving the years of varnish that build up both inside and outside the carbs.
1979 CB750K
1978 CB750 Four SS (gone but not forgotten!)
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Re: Carb Rebuild - 1981 CB750K

Ccheese4
In reply to this post by Ccheese4
I want to thank all of you for the replies! My #1 and #3 carbs are pretty gunked up with varnish, so I'll probably do the pinesol thing. I've heard about it, but was a little wary of doing so. But after so many positive responses, I'll probably give it a go.
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