Author Topic: 1978 CB550K Carb Rebuild  (Read 10969 times)

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Offline Jimbo4871

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Re: 1978 CB550K Carb Rebuild
« Reply #50 on: February 03, 2014, 10:04:31 AM »
Jason that set of rings is good.  I got the same set back in the fall from the same seller and they fit fine.  Hope everything else is going well.

Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #51 on: February 03, 2014, 10:13:41 AM »
Jason that set of rings is good.  I got the same set back in the fall from the same seller and they fit fine.  Hope everything else is going well.

Awesome! Thanks so much Jimbo! Will report back with the rebuild process when I get the new rings in.

Jason

Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #52 on: February 21, 2014, 07:37:07 AM »
Ok a couple weeks of travel later, and I'm ready to reassemble my carbs.

I have a question when it comes to setting float height.  From what I understand, the proper float height for these carbs is 14.5mm.  That is measured from the surface where the bowl gasket mates, to the highest point of the float when hanging in the normally mounted position. I have them all set  to 14.5mm +- 1mm which doesn't give the float a whole lot of travel, and doesn't let the the whole needle move hardly at all.  Basically the needle is bottomed out and the float just presses the spring loaded pin, in the center of the needle, in and out. 

Is this how the float needle relationship should operate, or should the entire needle be moving up and down a few millimeters?

At 14.5mm, when the carb is held upright, the bottom of the float is close to parallel to the bowl gasket mating surface.

I just don't want to get all this stuff buttoned up and back on the bike until I know its right.

Thanks!
Jason

Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #53 on: February 21, 2014, 07:00:00 PM »
Anyone know about this float height stuff?

Thanks!


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Offline Jimbo4871

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Re: 1978 CB550K Carb Rebuild
« Reply #54 on: February 21, 2014, 07:10:20 PM »
Jason I don't know or think you can adjust the float height on the 77-78 carbs.  I've never trided to check of adjust mine.  I do know each bowl has a over flow drain tube, the long brass tube that is in the center of the bowl.  It drains fuel if the bowl fuel level gets too high. 

Sorry I dont have more for you. 

Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #55 on: February 21, 2014, 08:20:20 PM »
No problem Jimbo!

Brian Barnes rebuild guide specifies the float height should be 14.5 as does the manual.

I just figured something out. I'm doing it all wrong! I should have read up on this whole float height process before asking. Sorry guys.

I'll be back if I can't figure it out still, but I think I'll be ok.

Jason


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Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #56 on: February 27, 2014, 07:40:18 PM »
Ok, another dumb question. I was am in the middle of reassembly and realized I cut the three black rubber tubes between the carbs during disassembly. They were cracked and I figured I would have to replace them anyway.

So my question obviously is what can I use as a replacement for these three tubes and where can I get it?

Thanks!
Jason

Offline dave500

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Re: 1978 CB550K Carb Rebuild
« Reply #57 on: February 28, 2014, 12:17:35 AM »
lawn mower/garden equipment repair places have good fuel hose,or a diesel pump and injector service place,your doing a great job there,90% of fixing an old bike up is cleaning parts,if you had a complete bike nos in every single part you could start putting it together in the morning and be riding it that afternoon.
« Last Edit: February 28, 2014, 12:25:47 AM by dave500 »

Offline Jimbo4871

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Re: 1978 CB550K Carb Rebuild
« Reply #58 on: February 28, 2014, 04:27:19 AM »
Ok, another dumb question. I was am in the middle of reassembly and realized I cut the three black rubber tubes between the carbs during disassembly. They were cracked and I figured I would have to replace them anyway.

So my question obviously is what can I use as a replacement for these three tubes and where can I get it?

Thanks!
Jason

Jason those x3 black rubber hoses are there to equalize the air in the float bowls.  That's the only difference between the 1977 carbs and 1978 carbs.  The 77' carbs didn't have those hose's, instead they just had a tiny tiny hole on the side of each carb to let air into the top of the bowls.  but if anything got in there it would clog up and screw up the pressure in the bowls.  so on the 1978 carbs they added the rubber hose's and inlet breather stem.  on your No.#2 carb you will notice two inlet stems on the side.  one is for fuel to come in from the gas tank.  the other is a beather inlet for the float bowls.  those rubber tubes connect all the bowls to this breather tube. 

SO...bottom line just take one of your carb bodies to a hard wear store and get any type of small hose that will fit snugly onto the cross tubes and size and cut it up when you get all x4 carbs together.  The only thing passing throw those tubes is air so you don't have to get anything special.   

Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #59 on: February 28, 2014, 05:42:17 AM »
Thanks guys!

I figured I could use any hose that fit but I just wanted to double check.  Of course I will have to use fuel line for the fuel, so I want this breather tubing to be black to match.

I'll take the carb body to Ace and have a look around.

Update with pics soon!

Thanks!
Jason

Offline brewsky

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Re: 1978 CB550K Carb Rebuild
« Reply #60 on: February 28, 2014, 08:36:27 AM »
No problem Jimbo!

Brian Barnes rebuild guide specifies the float height should be 14.5 as does the manual.

I just figured something out. I'm doing it all wrong! I should have read up on this whole float height process before asking. Sorry guys.

I'll be back if I can't figure it out still, but I think I'll be ok.

Jason


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I think there is some conflicting info on the float height for the 78 models. The manual says 14.5, chart says 12.5, and I think I've seen an addendum to the manual that says 12.5, but can't find it now. I set mine at 13 and it's good.
66 CA77
78 550K
78 CB750K
02 FZ1
09 GL 1800

Black 750K8

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Re: 1978 CB550K Carb Rebuild
« Reply #61 on: February 28, 2014, 08:49:05 AM »
Jason I don't know or think you can adjust the float height on the 77-78 carbs.  I've never trided to check of adjust mine.  I do know each bowl has a over flow drain tube, the long brass tube that is in the center of the bowl.  It drains fuel if the bowl fuel level gets too high. 

Sorry I dont have more for you.
This is what I don't get. Why give a setting if you can not adjust them :o I have PD carbs and you can adj. them but they are on a 750K 78 and you don't hold them straight up you tilt them when measuring the float. I guess they are a lot different.


Offline brewsky

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Re: 1978 CB550K Carb Rebuild
« Reply #62 on: February 28, 2014, 10:44:35 AM »
Both can be adjusted.
66 CA77
78 550K
78 CB750K
02 FZ1
09 GL 1800

Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #63 on: February 28, 2014, 10:47:11 AM »

No problem Jimbo!

Brian Barnes rebuild guide specifies the float height should be 14.5 as does the manual.

I just figured something out. I'm doing it all wrong! I should have read up on this whole float height process before asking. Sorry guys.

I'll be back if I can't figure it out still, but I think I'll be ok.

Jason


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I think there is some conflicting info on the float height for the 78 models. The manual says 14.5, chart says 12.5, and I think I've seen an addendum to the manual that says 12.5, but can't find it now. I set mine at 13 and it's good.

That was my plan. Just split the difference and go with it. With pod filters going on, I'd rather error on the richer side anyway.


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Offline AintNoEasyWay

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Re: 1978 CB550K Carb Rebuild
« Reply #64 on: February 28, 2014, 01:27:19 PM »
I have keihin pd41a carbs on my 750 k7. I think for the most part we've got similar carbs, just different scales & jetting.

Floats can be adjusted by manipulating the tang on the floats -- that middle metal part that the jet valve hangs from.

You should be fine going with anything between 12.5 & 14.5, as long as they're all the same height. My Clymer says one of the two, while the CB Shop Manual suggests the other. I think I went with the one that was in the shop manual.

Here's a video on it: https://www.youtube.com/watch?v=5aDMK1VFLyo

Offline dave500

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Re: 1978 CB550K Carb Rebuild
« Reply #65 on: March 01, 2014, 02:03:10 AM »
dont get too fussy on your float setting,picture whats going on inside the bowls when the bike is ridden,like hard braking or riding down hill,the fuel rushes forward,or cornering hard left or right,the fuel is side ways?or say powering away hard from a stop light,the fuel is backed up against the rear of the bowls and body over the gasket area,or just riding over rough roads,its a washing machine in there,do the best you can to be accurate but a millimetre aint critical!some guys have farted around to within .25 mm?you really think thats a make or break thing?it aint!just do the best you can and itll be fine,just think about how shook up the float is etc when its ridden,people read too much into the float setting as being critical,only idling and stationary,be sure not to lean your bike over too much at the next stop light,we cant have your precious float level out of kilter?
« Last Edit: March 01, 2014, 02:10:42 AM by dave500 »

Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #66 on: March 02, 2014, 05:57:29 PM »
DONE!  Kinda :)

So I finished assembling the carbs today! A few spots of rust that I couldn't remove, but if you compare them to the pics of when I first got the bike, I'd say they are looking better.  I just have to wait for my new main jets to come in, pull the bowls and install new jets (105's).  (I know currently the bowls are in the wrong spots. This is because I just slapped them on to protect the floats for now)

The only issue I ran in to is the choke plates rub again the carb bodies in a couple spots and cause the plates to remain open when I engage the choke. If I bump one of the plates, with the choke engaged, the spring will snap them down every time, but they always need a little help.  I would like to remove the plates and sand just a touch off the sides where they are rubbing, but the screws that hold these plates on are close to being stripped.  I don't know that they can take being removed again, let alone put back in. 

Not really sure what to do about that.  Here are some pics.




Also, the caps and bowls got my first attempt at polishing. Certainly not perfect, but look much better than had I just left them after soda blasting I think. 





Just want to say thanks again to everyone for the help and support!
Jason

Offline Jimbo4871

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Re: 1978 CB550K Carb Rebuild
« Reply #67 on: March 03, 2014, 05:46:48 AM »
They look Great Jason.  I had the same problem with my Choke Plates as well, and the near stripped screws. 

I did like you said.  I took them off and sanded the edges of the plates down a little.  I used hand sand paper, NOT A MACHINE GRINDER. 

I then took a stripped screw to a hardware store and got a set of new ones.  you can find them in hardware draws, where they sell individual nuts and bolts.  They are metric of course.

The carbs look awesome.  I hope they run as good as they look.   

Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #68 on: March 03, 2014, 07:34:35 AM »
Thanks Jimbo!

That was my only thought - Going to the hardware store to find replacement choke plate screws, but I wasn't sure that they were were standard enough to find easily, and I was afraid to take them off if I couldn't find new ones to go back on.

I think I will start by taking just one of the plates off, and using those two screws to find replacements before removing all the plates.

I hope they run as well as they look too!  I checked the bench sync just by looking at the slide height at closed throttle and they are all very close to slide number 2. Not sure I can get them any better without a vac sync.

I guess I will just give them a shot as they are now, and go from there.

Thanks!
Jason

Offline dave500

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Re: 1978 CB550K Carb Rebuild
« Reply #69 on: March 03, 2014, 11:45:14 AM »
any bench sync is a ball park set up,you wont get them any better without a vacuum sync,they arent synced now just set up close enough for starting and running so you can do a proper vacuum sync.

Offline AintNoEasyWay

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Re: 1978 CB550K Carb Rebuild
« Reply #70 on: March 04, 2014, 10:10:07 AM »
Thanks Jimbo!

That was my only thought - Going to the hardware store to find replacement choke plate screws, but I wasn't sure that they were were standard enough to find easily, and I was afraid to take them off if I couldn't find new ones to go back on.

I think I will start by taking just one of the plates off, and using those two screws to find replacements before removing all the plates.

I hope they run as well as they look too!  I checked the bench sync just by looking at the slide height at closed throttle and they are all very close to slide number 2. Not sure I can get them any better without a vac sync.

I guess I will just give them a shot as they are now, and go from there.

Thanks!
Jason

I think you'll be able to find replacement screws pretty easily. I put a little loctite on mine since the original screws on choke plates are peened after installation so they don't unscrew.

Offline redrider736

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Re: 1978 CB550K Carb Rebuild
« Reply #71 on: July 12, 2014, 07:24:07 AM »
Great rebuild thread.  Allot of help and info as I am in the process of rebuilding my 78's.......  One question I have is, I am having trouble removing my "slow jets" ? They are "pressed" in right??  I have tried to pull/twist out,  but they don't seem to want to come out?
78' CB550k (Not Run'n / Basket Case Project)
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Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #72 on: July 12, 2014, 07:26:47 AM »
Redrider, yep pressed in. I used a thin rag and small vise grips strait down on them. They're stuck pretty good but they'll come out without too much force


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Offline redrider736

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Re: 1978 CB550K Carb Rebuild
« Reply #73 on: July 12, 2014, 07:38:51 AM »
The carbs stripped down pretty easily until I got to the slow jets?  I was worried that I was doing something wrong....  I found a few great threads and read Brian Barnes clean/rebuild process halfway into my tear down and I don't remember reading that the slow jet needed  to come or can be removed? 
78' CB550k (Not Run'n / Basket Case Project)
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Offline jason405

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Re: 1978 CB550K Carb Rebuild
« Reply #74 on: July 12, 2014, 07:40:44 AM »
Well they can be. And should be cleaned. They are a VERY common culprit of tough idling hard starting problems when they are dirty


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