Topic: 1978 CB550K Carb Rebuild

[jason405]

Hey everyone, I am a relatively new member around here.  I post a while back about a CB350F I bought in pieces all the way down to the engine being split, and have since decided I don't have the time, nor the desire to start there with a first build. Also, I initially wanted a CB550 anyway, and when a friend offered to sell his 78 CB550K project bike at a reasonable price, I decided to switch gears and go with that. it is much closer to being able to at least run it to check things out.  All the main pieces are still on the bike, but the carbs/air box has been removed, are missing some parts, and the carbs are really dirty. 

So my first thought was ok I'll just rebuild them, only the PD46C carbs are about the hardest things in the word to find parts for and if you can find them, they are very expensive.  They are in good shape but are missing two of the four air needles and I need a new set of rubber intake boots along with gaskets and o rings.  The air box is missing boots too,  but I am going to run pods so thats fine. This is not going to be a performance bike.  Just an around the town cruiser. 

So the way I see it, I have two options.

1. Rebuild
 
Buy a cheap oversees carb kit http://www.ebay.com/itm/131074182637?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648 to get the 2 air needles, gaskets and o rings, and clean reuse all the rest of the factory brass parts.  I would also have to find and buy a used set of intake boots for the 78. Apparently they are slightly different from the pre 77 models.


2. Replace 

The other option I see is buy a used set of 74-76 model carbs http://www.ebay.com/itm/Cb550-carbs-carbutetor-complete-working-/261376101936?pt=Motorcycles_Parts_Accessories&hash=item3cdb3ace30&vxp=mtr and fit them to the 78 CB550k. Seems these carbs are WAY more common as are parts and rebuild kits. I can easily get a new set of intake rubbers to fit these, but I am assuming I will also have to get a new set of intake manifolds to match up with the older carbs? I understand the spacing of the intake manifold on the carb side is different on the 74-76 carbs, but is the engine side the same between the 74-78?   This is where I start to get grey.  Has anyone done this? Would this work ok?

 
I am just really ready to get the carbs back on it to try and fire it up, but I need some guidance on what initial direction to go.


Thanks so much!
Jason

P.S. I'll post pics of everything tonight if everything goes right.

[Bankerdanny]

If you are doing an around town bike then track down the carb and airbox boots, they will make tuning MUCH easier.

It is really rare for carbs to need actual rebuilding. Generally what they need is a very good cleaning and new gaskets and o-rings. The brass parts (jets and slide needle) should be reusable.

You can swap over earlier K or F carbs, but again I would track down the correct airbox rather than using pods and yes, you will need different manifolds and I think different throttle cables.

The PD's are fine carbs and have a fast idle cam to keep the idle speed up while the choke is being used, which is a nice feature.

[Destruckto440]

I've been working on my 78 cb550 for the last month or so. I bought the carb kit you mentioned on eBay. The o rings and gaskets are a little off on size but can be made to work. The rest of it seems to be ok. I've put a few hundred miles on my bike since rebuild no issues except it's a pain to get the float bowls to seal up with the supplied O rings.

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[harisuluv]

I can probably help you with some of those parts, like the air needles, gaskets, orings, etc.  The top is just a paper gasket so it isn't a crucial sealing surface, you can probably reuse yours.  There are different varieties of air needle, so pic is helpful.  Other brass parts I should have a surplus of already cleaned and ready for install.

You can also buy a lot of that stuff new from siriusconinc.com

I also think that Davidsilver spares carries the boots.  I know they have the airbox boot, not sure about the intake.

[harisuluv]

I've been working on my 78 cb550 for the last month or so. I bought the carb kit you mentioned on eBay. The o rings and gaskets are a little off on size but can be made to work. The rest of it seems to be ok. I've put a few hundred miles on my bike since rebuild no issues except it's a pain to get the float bowls to seal up with the supplied O rings.

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Cruzinimage carbs kits leave a lot to be desired.  I'm not a fan, I would recommend trying to order a la carte parts that are of quality and re-use as much OEM brass as you can.

I have no experience with the model kit you mentioned but the 350F kits that I got from them were a joke.  The float valve would depress and 1/5 times or so get stuck in that position.  Obviously the model you have has a different mechanism but that's my experience with the quality. 

[Destruckto440]

Yeah I bought the kit before I discovered this great forum. Live and learn.

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[dave500]

the ready to go ebay carbs may or may not be so ready to go aswell?

[jason405]

Whoa! Thanks so much for getting back to me. I am definitely leaning
toward rebuilding my existing carbs. Sorry when I say rebuilding, I
mean thoroughly clean them and all brass and in my case reuse as much
as I can.

I did not buy that ebay carb kit. It looked like such a good deal, but
I knew better and you all just firmed that up even more.

So I think first I will try to go the route of rebuilding my 46C
carbs.  So that in mind I am going to start disassembling them and
cleaning everything. I will take plenty of pics along the way and make
a list of what I find missing.

Harisuluv: that would be awesome if I could get those parts from you!
As soon as I get them torn down, hope tomorrow, I will get pics of
everything and those needles. I believe the spring washer and o rings
are missing for them as well.

And I will keep looking for the boots. I would like mot buy a decent
used set of the intake boots and if I could find the air box boots
great, but regardless I would like to end up with pods. I know it will
take more work to tune, I've read a ton of posts on it, but I have
read a few posts where people got it to work satisfactory.

In other news, I got the bike home today and started looking over
things. The tank has a "decent" rattle can job on it. But I got to
looking closer at the right side down low and there were some small
bubble spots. I scraped at them, and it became wet, and then revealed
a hole in the tank! Am going to strip and paint anyway so I sanded around the area to find where it looks to
have been patched in the past. Gas just started coming out! NOOOOO!
Not really sure what to do about that but we can save that project for
later   See the pic below.






Really not bad. Just really dirty.



All the bowls except one looks like this, pretty clean.  The one thats dirtier just has some hard crusted on film in the bottom.  Nothing that will win against my soda blaster



Notice the two missing air needles.






(I have the intake manifolds plugged with rags, but took them out for this pic)



You can see little spots around that hole that look like smaller holes that were also filled but haven't leaked yet.

[Black 750K8]

Your pictures are not working.

[jason405]

Thanks Black 750K8! Just noticed that and changed some things on my end. I think it should work now.

Jason

[dave500]

if you do use the earlier carbs youll need their manifolds aswell or you wont be able to vacuum sync them,yours have the vac plug on the carbs and a solid manifold,the early ones have the vac plug on the manifold.

[2strokeTrush]

You mentioned buying a 350f in parts?? Still have any your willing to " Part " With?

[jason405]

Ya I think for now I will try to use the existing carbs. Going to start cleaning them up today. Pics and update to follow.

Sorry 2stroke, I sold it back to the PO.

Jason

[jason405]

THanks calj737!

Like I said I was planing on stripping the tank anyway so I will do that at some point soon and go from there.  A high quality tank sealer will make a solid seal on those holes?  The tank does have plenty of gunk in it and I was just going to try a few methods I had read about. Apple cider vinegar, toilet bowl cleaner, electrolysis...  All these methods require filling the tank.  How will I temporarily patch these holes to do that? Tape?


The motor kicks through just fine.  I haven't drained the oil, but that is on the list.  It is obvious though, based on how oily and dirty the oil pan area is that is had been leaking.  I looked at the dip stick and it was wet but not super wet. 


I was just planning on changing the oil and getting the carbs back together to try too fire it, but I am like the sound of doing this motor "cleanse" you are describing.  What would the ration be to ATF and acetone and how much should I put in? Also I am assuming you meant "WITHOUT any spark" correct?

Thanks!
Jason

[jason405]

Ok awesome! Reguardless I was planning on pulling the pan when draining the oil, but I will for sure do the cleanse process first.

I will save the tank project for a little later. Will probably go ahead and fill it with apple cider vinager to start removing some rust and what.

Hoping to tear into the carbs tomorrow. Pics to follow if anyone is interested.

[jason405]

Ok, card rebuild update: I'm super excited! I managed to get the carbs torn down to the point of being able to dip them, and it was a very strait forward process. Remember, this is my first time doing any real work on a motorcycle

I have to give a TON of credit to Brian Barnes and his guide for rebuilding PD46A carbs!!! Although I have 46C carbs, they are so similar that I was able to follow his guide to the letter and everything came apart just as he said it should.  I was even able to get the stuck float pin out of the number 1 bowl using his troubleshooting section! He called just about everything I thought was going to be a "problem".

I stopped after tear down.  Next is clean up but I have a couple questions.

I understand that I can't dip anything with o rings.  They are all coming out because I am replacing them anyway, but I am wondering about the area where the  throttle rod goes through each carb. On each side of the carb there is what looks like a brass bushing and an o ring behind it.  Do I pull both of those pieces out of each carb?  See the pics below.






Had to use some PB blaster here.



Spring detail pic.



Number 1 coming off.



All but #3 off. Have to remove the throttle cam first.



They're free!



Worst bowl. Float pin was stuck but PB Blaster and Gumout finally got it out.



All other bowls looked like this one.



Nice and tidy.




This is the part I was talking about.  Does that bushing and o ring come out?




Also the needle guides are still in.  Do they have an o ring around them?  I have a can of chem dip ready to go!  Time to clean!

Thanks again for all the help guys!
Jason

[jason405]

Anyone know about removing these throttle rod bushings and o rings before dipping? 

Or weather or not the needle guides have to come out?

Also, how long should I dip each set of parts for? I was planning on dipping one carbs worth at a time so to not get them mixed up. 12 hours?

Thanks!
Jason


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[Jimbo4871]

Hello Jason. 
1st, I didn't get a chance to read through the entire forum here so sorry if I type anything anyone aready told you.

I have rebuilt my PD46Cs many times.  What are you using to dip your carbs? Yamaha Carb Cleaner.  That stuff works great but do NOT soak for more then 8 hours.  In the condition your carbs are in I would us Simple Green and scrub the hell out of them before dipping. 

I would seperate everything.  Brass parts you can soak almost for ever but all other metal type (the bowls, and main body for example) soak for no more than 8 hours,  Take out all bushings and anything not metal. 

I have used this website to order new jets and needles.  you'll have to dig a little but it's all there. 
http://www.jetsrus.com/a_jet_kit_street/honda_550_CB550_1977-1978.html

Stock jets size and setting: Slow is #42, main jet is: #90, and Needle setting is 2nd from the top. 

FYI: I think the only difference between the 77-78 PD46s is the float bowl air tube that runs between the carbs.  78 (PD46C) has them the 77 (PD46A) does not. 

Any thing else please feel free to email me. Jimencalada@gmail.com

[jason405]

Thanks so much Jimbo! I will use simple green first followed by Berrymans Chem Dip for a few hours.

I am just wondering how to get that bushing and I ring out that I show in my last picture?

Thanks!


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[Bru-tom]

as far as i know the brass bush is pressed in. There is a felt ring in there that creates a dust seal from the outside elements and prevent anything from entering.

When i did mine, i left the bush in place, saw no need to remove it (would end up damaging it i reckon). The felt i also left in place unless you can remove it carefully and soak it to get cleaned up. Otherwise there was a thread here somewhere on materials you can use to make new ones...

 

[jason405]

Ok great so I should avoid chem dip for the bodies then, just leave those pieces in place, and just use simple green on the bodies. Chem dip for all other small parts.

Thanks!


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[jason405]

Ok great so I should avoid chem dip for the bodies then, just leave those pieces in place, and just use simple green on the bodies. Chem dip for all other small parts.

Thanks!


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[Jimbo4871]

To get those rings out I used a very small very fine electric flat head screwdriver.  Some rings are felt and some are rubber.  leave the brass retaining ring in, don't try to force that off. 

For the Dip you are using you'll be fine leaving those rubber rings in, to soak the Carb Bodies.  However the Felt rings.....I would take them out. 

If you where using Yamaha Carb cleaner, all of your rubber and felt rings would be melted and dissolved after only a few hours. 

Carb dip is maid to clean and get ride of fuel deposits.  So using Simple Green to get rid of the dirt, rust, and what ever else you got going on will give the Carb Dip and better head start. 

I would also Highly recommend blowing out everything with an Air Gun after Simple Green, and Carb Dip. 

[Jimbo4871]

Sorry.  Fix in my last posting.  replace the word "Ring" with "Bushing".  except when I mention "Brass Retaining Ring". 

[jason405]

 Ok. Simple green for the initial crud cut, dip everything I can to dissolve in tight spots, then I will hit everything with the soda blaster like jets, ports, etc, then a final rinse.

I also used my die grinder and a fine disk to knock down a couple heavy rust areas.

Got started but it's going to take a while. Will report back once I get things cleaned.

Jason


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