Topic: 550F1 Carb Question.

[Frostyboy]

A question for the carburettor gurus among us. '76 550F1. I ordered carb kits from the States. The brand is K & L. The parts in the kit include 100 mains, 38 idles & the needles are stamped D26.
My carbs have 98 mains, 38 idles & the needles read 272304.
I can't imagine .02mm being too drastic a change for the mains as I'm changing from stock paper air filter to foam Unifilter, but I don't know about the needles. Do I have to mic them up to compare or is somebody out there familiar with needle numbers for comparison?

[wdhewson]

I don't know what the numbers are on your aftermarket needles.  As you say, "mic 'em". 

Lay the originals and new ones side by side and make 10 evenly spaced lines across both with a fine point felt marker.  Mic at each line and determine their similarity.  Keep in mind that small differences may not matter too much as the needle clip position changes the taper location quite a bit. 

Let us know what you learn.  Don

[05c50]

Is there anything wrong with your originals. I've had better luck using the original hard parts and only using the gaskets and o rings from aftermarket kits. When I measured the new aftermarket ones, the profile was different then the originals. Just my .02.

........Paul

[Deltarider]

1. Identify the engine in your bike precisely. Is it really a F or a K?
2. Read carb number: 069A is standard for F, 022A or 087A for a K.
3. Normally F's have needle 273004. That corresponds with Keyster D274.
    and normally K's have needle 272304 which corresponds with Keyster D26.
4. Did you order the right set?

[TwoTired]

Do you still have the stock exhaust?

If so, I'd just use the original stock parts, 98 mains and stock needles.

[Deltarider]

I'd prefer stock needles and jets too. Mine are stock, show no wear and have been in service over 130.000 km. What made you decide you need Keysters?

[Frostyboy]

Thanks for all the responses. I'll have to wait til I get carbs back from soda blasting & dipping to see numbers on carbs themselves.
I ordered kits from CRC2 last year, they made it read like one kit fits all, but now I realise Aussie models are different from USA. Are K & L what you guys are calling Keysters?
I wanted to replace jets cos I have little faith in PO. I'm just not sure if he's reamed 'em out or not. From what Deltarider said, my carbs already had K needles so I don't know what's goin' on.
By the way, are the idle air screws supposed to have o rings fitted? It looks like there's provision on the head of the screw.

Oooh, I've just found http://forums.sohc4.net/index.php?topic=1925.0
I'll have to read this a few times & come back.

[Frostyboy]

2. Read carb number: 069A is standard for F, 022A or 087A for a K.

Okay, I got the carbs back today, all bright clean & shiny. The number on the mounting flange reads 627B.
So does that mean a 550F1 has different carb to a 550F?
David Silver has a kit specified for an F1 & it contains 98 mains & 38 idles but no spec for the needle. Methinks it might be the right kit for me though.
Any thoughts?

[Deltarider]

Now it gets a bit complicated because 627B carbs belong on a CB500 Four.

[TwoTired]

The stamping on the carb body relates to the internal parts used when first sold.  It describes a set up number, where the main jet, pilot jet, main air jet, pilot air jet, slide needle type/position, emulsion tube hole size/quantity and placement, throttle valve orifice, and pilot screw taper all conform to tuning parameters for a specific model machine.
For all the US CB550 F models with the four into one exhaust system, that carb stamping was 069a.
Carbs stamped 627B were intended to be used on the CB500.

After market kits generally offer commonly replaced components and are not intended to convert the internal set up from one type to another, only repair a specific model or set up type.

I have never found an exhaustive list or description from Honda that specifies exactly what changes are made internally among the different carb internal set ups.  I began to make measurements of internal components to determine these internal differences with the carb types side by side.  But, my data is incomplete, as finding original, unmolested carb sets has become rather difficult, and some of the specimens I have are somewhat suspect.  People routinely change these internal parts and don't change the stamping numbers.

Finally, many people assume that because the carbs look the same on the outside, they are also the same on the inside, which is decidedly NOT so.

[Deltarider]

TT, I've collected in a scheme most carbdata of the 500/550 series but so have you probably. Let's see if we can establish a complete overview and remove data that are corrupt. For instance: I've no knowledge of CB500s equipped with 022A carbs. Are there any?
Another example: in an existing overview I read an airscrew position of 1¹/₂ (again CB500) out, yet I've not found any Honda source for this.
Most data you have already, I suppose. Sometimes data are conflicting, even in Honda's own material. Maybe, with the help of others, we can clear things up.

Anyway, to start here are some data that are not in any overview.
They concern the 649A carbs that are on the models CB500, CB500K1 and CB500K2 area code [ED, G, H]. BTW, the CB500K2 here was different from the 500K2 in USA. Our K2s were on the market in 1976 and 1977.
The 649A is an old style Keihin carb
main jet #78,
slow jet #40,
needle set 16012-323-004
needle 272304 has 5 grooves, standard is 3rd (middle) position
air screw: 16016-323-004 (1.2, hollow tip, cross drilled)
recommended position: 1 ⁺/_- ¹/₈ out

(floatparts and floatlevels are the same for all 500/550 models that have old-style carbs.)
I recommend anyone if possible to start with stock. Correct overviews and Parts Lists are essential. As you've seen in the posts above, there's a need. Therefore I've offered Einyodeler to upload my copy of Parts List 3 CB550F2 (1978), but so far have received no reaction. I also have copies of other Parts Lists but they can be found at our Italian friends of Honda4fun http://www.honda4fun.com/spaccati/spaccati.html.

[Frostyboy]

Thank you TT & Deltarider. By what you have told me it appears that my lack of faith in PO was perhaps well founded. Detuned by an expert it may seem.
The bike certainly appeared to run reasonably well before I let it sit for 4 years + & I've owned it for 20 years all up, so I'll rebuild with existing hard bits as has been advised & leave it be. I'll give it a run & pull the plugs at various stages & take it from there.
Thanks again for your input. I hold your experience in high esteem.
Do you think if I start with the clips on the middle position, it'll give me 2 ways to go?

[Deltarider]

Do you think if I start with the clips on the middle position, it'll give me 2 ways to go?

That's what I would do, yes.
Don't be discouraged, your bike will run. Modifications between various carbs of the 500/550 series are minor anyway. Just give it a try.

[TwoTired]

TT, I've collected in a scheme most carbdata of the 500/550 series but so have you probably. Let's see if we can establish a complete overview and remove data that are corrupt. For instance: I've no knowledge of CB500s equipped with 022A carbs. Are there any?

I don't believe so.  The 022A carbs were all found CB550K 74-75.  And perhaps some 76 models, but these are often found with 087A setups.
The Honda Shop manual adds confusion with what I believe is a misprint.  In Chapter 16 title supplement to CB550F, and published AFTER the CB550K1 supplement, it describes differences between the F models and the 550 K models.  Prior supplements describes differences between CB500 and CB550.  The table in section 16, labeled "Carburetor setting table" has a list of settings for the 069A for the F model and lists the settings for the 022A carbs as well.  I believe they meant to compare the CB550 to the CB550F carbs.  So, the CB500 Column heading should read CB550.
The CB500 Carb set up has its own data chart in Chapter 4 near section C.  This was originally printed when there was no need to differentiate between later models as they didn't exist (and wouldn't have if the model didn't sell well).  So, the Shop manual does not have the 627A (or B) set up numbers listed because at the time there could be only one set up/carb type on the CB500 (circa 71-73).

Another example: in an existing overview I read an airscrew position of 1¹/₂ (again CB500) out, yet I've not found any Honda source for this.
Most data you have already, I suppose. Sometimes data are conflicting, even in Honda's own material. Maybe, with the help of others, we can clear things up.

I've summarized many of my findings, and they appear in a chart posted in the CARB FAQ:
http://forums.sohc4.net/index.php?topic=5410.0

From the Carb table in section 4 of the Honda Shop manual, the air screw opening S/B 1 +/- 1/8 turn.  This, presumably, would apply to the 627 carbs of the CB500.  The CB550 Carb's air screw (K or F)would be set to 1 1/2 +/- 3/8 turns out as specified in later supplements and corroborated by a little tune up booklet published by Honda referencing the CB550, K1, 76  (which also matches the Chapter 16 shop manual supplement, btw).

Anyway, to start here are some data that are not in any overview.
They concern the 649A carbs that are on the models CB500, CB500K1 and CB500K2 area code [ED, G, H]. BTW, the CB500K2 here was different from the 500K2 in USA. Our K2s were on the market in 1976 and 1977.
The 649A is an old style Keihin carb
main jet #78,
slow jet #40,
needle set 16012-323-004
needle 272304 has 5 grooves, standard is 3rd (middle) position
air screw: 16016-323-004 (1.2, hollow, cross drilled)
recommended position: 1 ⁺/_- ¹/₈ out

(floatparts and floatlevels are the same for all 500/550 models that have old-style carbs.)

I simply have no data source or experience with the 649 carbs.

I have started a spread sheet (actually expanded on the the one in the FAQ), which includes the actual measurements of the internal components.  Slide needle tapers, lengths widths, air jet diameters, emulsion tube jet and bleed hole parameters, etc.
I update this list as I encounter carbs sets that have credibility as being original.  The chart does NOT include all the set up numbers yet, so remains unfinished.
This is a "reverse engineering" effort, as actual verifiable data from Honda is not forthcoming.

If you wish, I can add the data you've listed for the 649s to my chart before I publish the new replacement for the FAQ.

Cheers,

[TwoTired]

Thank you TT & Deltarider. By what you have told me it appears that my lack of faith in PO was perhaps well founded. Detuned by an expert it may seem.
Do you think if I start with the clips on the middle position, it'll give me 2 ways to go?

I'm going to back up and ask for foundation data, before making a recommendation.
Are you sure you have an CB550F1?
By US standards, this would be a 1976 model with a 4 into 1 exhaust system.
Does it still have the stock exhaust system installed?
If not, this may explain why you no longer have the stock 069a carbs on it, as book value carb set ups would no longer apply.  (for ANY carb set you put on it, since the engine breathing characteristics are no longer stock.)

[Deltarider]

I believe they meant to compare the CB550 to the CB550F carbs.  So, the CB500 Column heading should read CB550.

Your observation is correct. Must be a misprint. I believe there's no other source that suggests 022A carbs for the 500.

From the Carb table in section 4 of the Honda Shop manual, the air screw opening S/B 1 +/- 1/8 turn.

This setting is found in practically all manuals. Yet Honda adds confusion on p 9 (Maintenance Operations) in the Workshop Manual where Honda suggests 1⁺/_- ³/₈. I don't know what to think of that.

If you wish, I can add the data you've listed for the 649s to my chart before I publish the new replacement for the FAQ.

That would be nice. By comparing with other models one sometimes can detect the logic (if one is lucky). For instance: I'd like to know the difference between 627A and 627B carbs. BTW, just a year ago I've discovered a difference between the #3 and #4 float bowls on my 649A carbs. But I'll take pictures first.

corroborated by a little tune up booklet published by Honda referencing the CB500, K1, 76  (which also matches the Chapter 16 shop manual supplement, btw).

Do I read well that in forsaid tune up booklet there's no other or extra information than offered in the Workshop Manual? And that it is referencing the CB500, K1, 76? (just to make sure: K1, 76 meaning... 550s?)
The other day I asked our French friends of the 'Amicale des Honda CB et Four' what they mean by 'one turn', 180^o or 360^o? It's because on their site one reads 2 ⁺/- ¹/₈. Turns out to be the wrong info, originated by just one corrupt 'manual d'atelier' (workshop manual).

[Frostyboy]

Are you sure you have an CB550F1?
By US standards, this would be a 1976 model with a 4 into 1 exhaust system.
Does it still have the stock exhaust system installed?

When I purchased this machine I was told it was '75 CB550F. When some inappropriate parts arrived from David Silver I supplied them with VIN & Engine numbers. It was they that informed me it's actually a CB550F1. Riveted plates with build date didn't come into vogue until the 80's in Aus I believe, so there's no date to be seen anywhere on the bike.
If I pm you these numbers are you able to identify the model? (I'd hate to think someone might steal my bike's identity lol.)
Yes it does have 4 into 1, but pipes come down both sides of the oil filter, not all to the right like in Honda's promo poster I've seen around the place. I believe the muffler might be Road Hawk megaphone style.
Cheers.

[TwoTired]

From the Carb table in section 4 of the Honda Shop manual, the air screw opening S/B 1 +/- 1/8 turn.

This setting is found in practically all manuals. Yet Honda adds confusion on p 9 (Maintenance Operations) in the Workshop Manual where Honda suggests
1⁺/_- ³/₈. I don't know what to think of that.

I don't know.  I do think the salient point is that the adjustment for the 627 carbs was centered at 1 turn out.  Whereas, the CB550s are 1 1/2 turns.  Logically this makes sense since the larger displacement should draw a deeper vacuum, to maintain A/F mixture more air is added to the premix in the pilot circuit.

corroborated by a little tune up booklet published by Honda referencing the CB500, K1, 76  (which also matches the Chapter 16 shop manual supplement, btw).

Do I read well that in forsaid tune up booklet there's no other or extra information than offered in the Workshop Manual? And that it is referencing the CB500, K1, 76? (just to make sure: K1, 76 meaning... 550s?)[/quote]

You read it well.  I just stutter fingered the reference.  S/B 550 not 500.  I made the edit to my post.  Thanks for the catch.
I wish I had the whole booklet.  But, I only have these two scanned pages and the cover that have been posted to this forum previously.

[TwoTired]

If I pm you these numbers are you able to identify the model? (I'd hate to think someone might steal my bike's identity lol.)
Yes it does have 4 into 1, but pipes come down both sides of the oil filter, not all to the right like in Honda's promo poster I've seen around the place. I believe the muffler might be Road Hawk megaphone style.

The stock CB550F header swoops all the head pipes over to the right side of the oil filter.  The single muffler was large and very quiet.  It's restriction is likely why the mains were only #98 in size due to the exhaust pressure build up in the muffler at very high RPM/speed.  The Slide needle was also clipped in position two to lean the midrange for the 069a carbs.

Since your exhaust setup is a generic one-size-fits-all replacement, it is probably intended for the 550K model.  If they did their engineering right, the jetting and set up for the carbs would be same as the 022a or 087a carbs.  I would take my tuning direction from those carbs on your bike rather than the 069a carbs.  You can find the stock set up/adjustments/settings in the carb FAQ chart.
I would expect #38 Mains and #100 jet would work fine for your bike.
The unknown is the emulsion tube and slide needle parameters, which are for tailoring the mixture between 1/4 and 3/4 throttle positions.  I don't know precisely what, if any, differences exist between the emulsion tubes, and slide needle of 627b carbs are compared to the 022a or 087a carbs.  I haven't gotten around to measuring my examples yet.  (I'm loathe to taking apart good, working carbs, just to obtain measurements.)
If these components are the same in machining dimensions, then you should put the needle clip in the 4th position from the top.
Anyway, your bike is now a hybrid, and you will have to find the correct carb settings for the mods made to the bike.  Book settings may or may not apply, depending on what the exhaust manufacturer intended.  Now is the time to choose an air filter type stock or not, and then tune the carbs to the inlet, exhaust an engine breathing requirements of the existing engineered set up.

Below is my scanned page for CB550F model identification published by American Honda.  (So, you don't have to give away your bike's identity.)

[Deltarider]

TT, thanks for posting those pages.

The unknown is the emulsion tube and slide needle parameters, which are for tailoring the mixture between 1/4 and 3/4 throttle positions.  I don't know precisely what, if any, differences exist between the emulsion tubes, and slide needle of 627b carbs are compared to the 022a or 087a carbs.

According to the Parts Lists 627B, 649A, 022A and 087A carbs all share the same needle set. The set includes needle and emulsion tube. So if they have the same part number, it's safe to assume sets are identical. Clip position may (and does) vary for the forsaid carbs. I presume the Carburetor setting table on p165 in the Workshop Manual offers a correct description. That is: after correcting CB500 (clearly a mistake) for CB550 in the left column. That table mentions "4 grooves" (CB550) and "2 grooves" (CB550F-A). I believe we're witnessing a Japanese struggle with the English language here and that the Manual means to say 4th and 2nd groove respectively. Would be nice if we can have an comprehensive overview without errors and where pictures appear when clicked at the part in the table. The photo of the "screw set A" above is just a start. I hope to add more pics in the future.
What we know for sure is that the needle set of the F models differ from the K's and that of the K's the 087A carb is the only one that shares the "screw set A" [16016-390-004] with the F's. BTW, is that a solid type screw without a crosshole?

[TwoTired]

What we know for sure is that the needle set of the F models differ from the K's and that of the K's the 087A carb is the only one that shares the "screw set A" [16016-390-004] with the F's. BTW, is that a solid type screw without a crosshole?

Yes, the 069a carbs had solid tipped air bleed screws with a different tip angle.

I just checked my spare set of 087a carbs.  They have hollow tipped air screws.  But, I can't verify their originality.  So far, I can't measure anything different about them from an 022a carb.  My 087a carbs may have been previously molested.  But, they are the only ones I have with those stamps.

Where did you find specs. for a CB550K2?

[Deltarider]

Where did you find specs. for a CB550K2

I have since long the original Honda Parts List (1) CB500K2 [ED, F. G] May 20, 1976.
Maybe it would be better to call that model CB500K2 '76 as it's unlike the US K2 and shares many things with the 550K2 '76. Anyway that Parts List can be opened or download at Honda4Fun http://www.honda4fun.com/spaccati/spaccati.html. It's the one titled  CB500 prodotto fino al 1976.
The only Parts List I haven't seen at Honda4Fun or anywhere else on the internet is the CB550F2 November 20, 1976 (at the bottom of every page it says _1978.07.20). I have a paper copy and offered Einyodeler to upload it. The other I have in paper is the CB550F/CB550F1 Parts List (3) November 20, 1975 (at the bottom of the pages _1976.07.10). It differs between the 550F and the 550F1, so offers more than the CB550F Honda4Fun has.

[Frostyboy]

Wow, I never really expected to start a marathon here, but you guys are awesome.
From your model ID chart TT, it appears that I have a '75 frame # but the engine # and everything else seems like '76. I still don't know where 'F' 'F1' 'F2' etc come into it.
I'll kit the carbs with the 100 mains and the original needles. I had dropped the needles to the 2nd from the top years ago in an effort to get away from bogging off the line, I thought it was from overfuelling, but it turned out to be a mongrel hot rod cam. Ran sweet once I replaced the cam with a standard one & I never worried about resetting the needles.
It's still some time off getting back on the road, but your assistance here is terrific. I'll have to make another donation to the board in appreciation.
Cheers.