Author Topic: 1977 K8 carb question (Read 2090 times)

kjdelaney · « **on:** April 03, 2013, 02:02:43 PM »

I just spent 30 minutes looking but i still cant find the answer to my question. I have a 77 CB750 k8. It is running way rich. I need to use starter fluid to get it to start and when it is running the exhaust fumes are very strong . I think the fuel mixture may have something to do with the difficulty starting. I really don't want to pull the carbs off again if i don't have to. Isn't there a screw that i can turn to adjust the air fuel mixture somewhere on the carb? If so which one?

flybox1 · « **Reply #1 on:** April 03, 2013, 02:06:06 PM »

the fuel mixture screw is centered on the front(engine) side of the carb at the bowl seam. its between the bowl corner screws. shrouded. clockwise makes it LEANER.
check this thread.
top picture has the fuel mixture screw in the foreground. (of course this is a picture of the carbs upside down on a bench)
second picture shows the mixture screws tucked up along the bowl seam. shrouded
http://forums.sohc4.net/index.php?topic=101647.0

kjdelaney · « **Reply #2 on:** April 03, 2013, 02:15:39 PM »

The screw located on the bottom front correct?

flybox1 · « **Reply #3 on:** April 03, 2013, 02:18:07 PM »

of the top picture in that thread, yes.
besides the smell, what else makes you think its rich?
what do your plugs look like?
what is your intake and exhaust config? jet sizes? needle clip position? bowl fuel level?

lucky · « **Reply #4 on:** April 03, 2013, 04:46:40 PM »

Those are the exact symtoms that manifest when the idle jets are clogged.

Stev-o · « **Reply #5 on:** April 03, 2013, 07:57:33 PM »

You def have a carb issue. Do you recently rebuild them including new jets?

kjdelaney · « **Reply #6 on:** April 04, 2013, 03:57:40 AM »

I did rebuild but reused the jets. New gaskets and cleaned the crap out of it. It was very dirty on the outside. I adjusted the floats and cleaned the inside the best i could without taking it completely apart. One thing i didn't do was mess with the jets or the needles. In hindsight i wish i had. As far as their sizes i couln't tell you what was in there. I figure if this doesn't work that would be my next step. Take them out and replace them. Maybe put smaller ones in. im aslogetting some backfire on deceleration.

kjdelaney · « **Reply #7 on:** April 04, 2013, 03:59:58 AM »

Quote from: flybox1 on April 03, 2013, 02:06:06 PM

the fuel mixture screw is centered on the front(engine) side of the carb at the bowl seam. its between the bowl corner screws. shrouded. clockwise makes it LEANER.
check this thread.
top picture has the fuel mixture screw in the foreground. (of course this is a picture of the carbs upside down on a bench)
second picture shows the mixture screws tucked up along the bowl seam. shrouded
http://forums.sohc4.net/index.php?topic=101647.0

When you posted your first reply i went out to the bike and looked. That was the one i thought it was. Thanks for the help!

Stev-o · « **Reply #8 on:** April 04, 2013, 05:02:37 AM »

Why wouldn't you "mess with the jets or the needles"? Probably the most important thing when rebuilding carbs.

flybox1 · « **Reply #9 on:** April 04, 2013, 06:45:14 AM »

Quote from: Stev-o on April 04, 2013, 05:02:37 AM

Why wouldn't you "mess with the jets or the needles"? Probably the most important thing when rebuilding carbs.

+1

lucky · « **Reply #10 on:** April 04, 2013, 07:04:45 AM »

Quote from: kjdelaney on April 04, 2013, 03:57:40 AM

I did rebuild but reused the jets. New gaskets and cleaned the crap out of it. It was very dirty on the outside. I adjusted the floats and cleaned the inside the best i could without taking it completely apart. One thing i didn't do was mess with the jets or the needles. In hindsight i wish i had. As far as their sizes i couln't tell you what was in there. I figure if this doesn't work that would be my next step. Take them out and replace them. Maybe put smaller ones in. im aslogetting some backfire on deceleration.

You do NOT have to replace the jets.
Just clean them and make sure you can see daylight through them.
The idle jet is a pull out jet.
Remove the float first so you do not damage it, and grab the jet with small vice grips or pliers and pull while twisting.

iron_worker · « **Reply #11 on:** April 04, 2013, 08:04:35 AM »

Agreed with above. Get those jets out of there! Clean the idle jet and main jet/emulsion tube. (There is an emulsion tube on the idle as well but it's built into the jet itself ... small holes along the side.)

The idles can plug up soooo easily with such small passages. You probably knocked some dirt loose while cleaning and possibly made them worse than they were before.

IW

750K · « **Reply #12 on:** April 04, 2013, 09:03:56 AM »

You have to pull the idle jet out to really get the passage way clean, spraying carb cleaner throug them while still in the carb body won't get all the crud out. Just be gentle when you ease them out and put them back in, you don't want to damage either the jet or the hole in the carb body.

Stev-o · « **Reply #13 on:** April 04, 2013, 04:29:51 PM »

I have not had to clean the carbs on my K8, are the mains removable? pressed in, right?
(I'm more familiar with the earlier carbs).

Did Honda do this as an EPA thing so we wouldn't change them?!

750K · « **Reply #14 on:** April 04, 2013, 04:54:48 PM »

Iirc Stev-o mains on the 78's are screw in, only the idles are press in. At least that's the way my pd's on my 77 are, I have a set of 78 pd's as spares and I'm almost certain the mains are the same as the 77's but it was last summer I had them apart...

flybox1 · « **Reply #15 on:** April 04, 2013, 04:57:11 PM »

The mains are screw in. They screw in to the emulsion tube, which screws into place. Pilots are press fit.

Stev-o · « **Reply #16 on:** April 04, 2013, 05:37:49 PM »

Ok, so the idles are pressed in, got it. Thx

kjdelaney · « **Reply #17 on:** April 04, 2013, 06:00:29 PM »

Quote from: Stev-o on April 04, 2013, 05:02:37 AM

Why wouldn't you "mess with the jets or the needles"? Probably the most important thing when rebuilding carbs.

Cause im a noob.....

That and i was distracted by all the other CRAP that was on them.... These things were caked in 36 years of grease! I think i'm just going to pull them off again. I'm sure it could use more TLC. Or should i try the screws?

Stev-o · « **Reply #18 on:** April 04, 2013, 07:16:09 PM »

Please understand no disrespect was intended. Yes, pull em off and call it a lesson learned. Either clean the jets spotless or buy new ones.

flybox1 · « **Reply #19 on:** April 04, 2013, 07:38:19 PM »

Pull your carbs and do it right. It's tough to harm brass jets. Clean them well and reuse them

lucky · « **Reply #20 on:** April 04, 2013, 07:41:13 PM »

Quote from: Stev-o on April 04, 2013, 04:29:51 PM

I have not had to clean the carbs on my K8, are the mains removable? pressed in, right?
(I'm more familiar with the earlier carbs).

Did Honda do this as an EPA thing so we wouldn't change them?!

The mains are easily removable.
Only the idle jets are pressed in.
The EPA just made honda do what they wanted to keep owners from making any changes.

bollingball · « **Reply #21 on:** April 04, 2013, 08:00:33 PM »

I keep looking at the title to this

is it a 77 or 78 K7 or K8 kjdelaney I don't think there are very many people that got there carbs right the very first time. So don't feel to bad. Like everyone said the slow or pilot jets must come out.
Ken

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Author Topic: 1977 K8 carb question (Read 2090 times)

bollingball