Author Topic: Compulsive Carburetor Questions Re: '76 CB550F  (Read 11459 times)

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Offline nopivnick

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Compulsive Carburetor Questions Re: '76 CB550F
« on: June 14, 2005, 02:50:27 PM »
I'm trying to get my head around this Keyster vs. OEM jet/needle and carburetor tuning business. So far I've found only two applicable Keyster Carburetor Kits for the CB550 Keihin 069A Carburetors:

KEYSTER Repair Kit: KH-0151
Original Kit Number: 16100-390-004
Applicable Car Model: HONDA CB550F ('75,'76,'77)
Main Jet Size: #98
Slow Jet Size: #38
Needle Size: #D274

KEYSTER Repair Kit: KH-0128
Original Kit Number: 16100-374-004
Applicable Car Model: HONDA CB550
Main Jet Size: #100
Slow Jet Size: #38
Needle Size: #D26


Questions:

1.) Are there any other Keyster Kits with usable bits?

2.) With any air filter / intake setup that is less restrictive than stock (in my case K&N pods) am I correct in assuming the Main Jets will necessarily need to be larger than either the #98 or the #100 Main Jets supplied in the Keyster Kits described above?

3.) It would appear most people end up drilling out / enlarging the stock size jets rather than hunt down and/or pay through the nose for irregular Jet sizes. Do people drill out / enlarge Slow Jets also?

4.) Can anyone tell me how to interpret the differences between Keyster Needle Part Numbers #D274 and #D26?

5.) The needles in my carburetor are all stamped: 273004. Are they OEM needles? The '004' smacks of HONDA part number sequences for Keihin Carburetors, but '273' is way off for an appropriate HONDA model number. Furthermore, all my jets are stamped with a symbol that resembles a 'K' shaped balloon-like outline. Is that a 'K' for Keihin? Keyster? K&L?

migopod

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #1 on: June 14, 2005, 03:49:18 PM »
i am also interested in the font of wisdom here.  I called my parts people last week to see if they had a different
kit for 550k and 550f, and they said that K&L only lists the cb550 fours for that model*, and they didn't think that
OEM kits were still available.

How possible is it to get OEM kits (preferably not via eBay)?


* which is to say that there wasn't a separate kit for F and K
« Last Edit: June 14, 2005, 05:02:45 PM by migopod »

Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #2 on: June 14, 2005, 09:01:52 PM »
* which is to say that there wasn't a separate kit for F and K

On the contrary, from what I've deduced that's precisely the difference between the two Keyster Kits.

KH-0151 is a Keyster replacement for Honda's OEM Kit 16100-390-004 (The CB550F Product Code is 390)
KH-0128 is a Keyster replacement for Honda's OEM Kit 16100-374-004 (The CB550K Product Code is 374)

Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #3 on: June 15, 2005, 11:10:24 PM »
3.) It would appear most people end up drilling out / enlarging the stock size jets rather than hunt down and/or pay through the nose for irregular Jet sizes. Do people drill out / enlarge Slow Jets also?

I gather from a statement on this page http://www.salocal.com/sohc/tech/carb/asmpg_mgs/jetgraph.htm the answer is no.


4.) Can anyone tell me how to interpret the differences between Keyster Needle Part Numbers #D274 and #D26?

A swell guy named Harry wrote me back regarding this question:

Yes sir the numbers are actually from Keyster so we can keep a database. The
Cross reference to Keihin's needle are below. However we do not have the
formula of the taper for these needles, but the if model should be a
slightly thinner taper for better fuel flow sir.

D274  = Keihin 273004
D26 =  Keihin 272304



5.) The needles in my carburetor are all stamped: 273004. Are they OEM needles? The '004' smacks of HONDA part number sequences for Keihin Carburetors, but '273' is way off for an appropriate HONDA model number. Furthermore, all my jets are stamped with a symbol that resembles a 'K' shaped balloon-like outline. Is that a 'K' for Keihin? Keyster? K&L?

Based on Harry's response, I gather needles stamped with 273004 are KeiHin/OEM.


Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #4 on: June 15, 2005, 11:11:35 PM »
Heh. Ever get the feeling you're talking to yourself?


Offline TwoTired

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #5 on: June 16, 2005, 12:01:19 AM »
Heh. Ever get the feeling you're talking to yourself?

yes, frequently. :-X
Lloyd... (SOHC4 #11 Original Mail List)
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Offline oldbiker

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #6 on: June 16, 2005, 01:40:54 AM »
Heh. Ever get the feeling you're talking to yourself?


only when my wife is about.

Offline Mark M

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #7 on: June 16, 2005, 06:26:29 AM »
My wife told me I was to stop talking to myself.

I think thats why she rarely stops for air herself........still, in the shed with the radio on (an angle grinder works well too) I can almost block the sound out.  :o
In the UK anything over 40 years old only needs insurance and Fuel.

Offline bryanj

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #8 on: June 16, 2005, 08:15:23 AM »
Talking to yourself is no problem its when you start answering youself and start arguing that you really need to give up!!!
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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migopod

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #9 on: June 16, 2005, 09:24:17 AM »
I've heard some pretty bad things about keyster jets, and what i'm wondering is if using
size 100 jets and equivalent needles from the K&N kit for the 550(unspecified) four would be
better than using 98 jets and equivalent needles from keyster.

I've got the 100 jets in the rack now, and i was about to put it back in the bike after dipping
and whatnot, but if i'll just end up needing to pull them back out to redo the needles and main jets,
i'd rather not put them in.

What are the thoughts?

Offline TwoTired

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #10 on: June 16, 2005, 10:24:15 AM »
I can't remember what configuration you're bike is in.  If stock, I think you are better off with the stock sizes of jets and needle profiles.  I've seen no characterization or descrption of needle profile beyond the "different" statement.  Wouldn't it be nice to see a chart or graph noting flow vs. position?

I have yet to see the stock needles wear on any of the CB500/550 carbs I've taken out.  Same is true for the jets.  And, fortunately, I've not encountered any that were drilled.

While o ring replacement is routine, I haven't seen a need to replace the OEM carb components which proved to work well when the bike was in it early years of operation.

But, if your bike is modified then I think it is fit-&try-read-plugs-adjust, and repeat 'til you're satisfied with how it all works.

Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

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Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #11 on: June 16, 2005, 11:04:45 AM »
I can't remember what configuration you're bike is in.  If stock, I think you are better off with the stock sizes of jets and needle profiles.  I've seen no characterization or descrption of needle profile beyond the "different" statement.  Wouldn't it be nice to see a chart or graph noting flow vs. position?

Would it ever! I assumed the best place to find this info would be from Keyster directly but I can't seem to find any official manufacturer/company web site, let alone technical pages, for them. KeiHin posts something like that for their aftermarket racing needles < http://www.keihin-us.com/needle.htm > but unless I'm mistaken none of these needles are for the 550's 069A carbs.


But, if your bike is modified then I think it is fit-&try-read-plugs-adjust, and repeat 'til you're satisfied with how it all works.

Here's a nice little warm & fuzzy thought:

If there were enough CB550 owners (we seem to be the neglected, bastard carburetor/displacement child of the bunch) with an ongoing interest in carb tuning variables, we could all toss in a few dollars and assemble a sort of comprehensive, roaming sohc4.net carb-tuning kit with all the applicable jet and needle sizes from different manufacturers. Then you just 'sign up' for it and when you're done pulling your pud, you pass it along to the next guy.


Offline TwoTired

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #12 on: June 16, 2005, 12:21:54 PM »
While bumbling around the internet, I stumbled upon this interesting bit:
http://www.sudco.com/keihin_jn.html

It is hard to read.  But, there is a small chart showing what part of the needle dimensions are dominant for specific throttle positions.  This might be helpful if you are trying to taylor your needles for your specific engine, pipe, air filter set up.

The bottom of the chart reads ( I think)  1/8, 1/4, 1/2, 3/4, and WOT for throttle opening
The vertical axis read Taper, L1 and Clip position, and diameter. 

This could be a clue as to what changes you need to make to your carbs if your mixture isn't right at specific throttle positions.

Anyone have these charts in an easier to read form?
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

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Offline kghost

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #13 on: June 16, 2005, 12:45:56 PM »
If your worried about Stock vs aftermarket needles, You can use a drill gauge to compare taper. Bob Wessner used my suggestion when comparing 750 needles. Interesting result, as the aftermarket was pretty different.

Stranger in a strange land

Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #14 on: June 16, 2005, 12:50:04 PM »
Anyone have these charts in an easier to read form?

http://www.sudco.com/catalog105/116-117.pdf

The chart you refer to scales cleanly if you bump up the magnification/view, not so much the 'needle dimentions' graphic to the left but nothing new there anyway.

Damn, brother. Good eyes! I'd already poured over that site looking for any new info and missed that little bit.

Holy Digital Archival Forensic Carburetor Nerdification, Batman!

Offline TwoTired

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #15 on: June 16, 2005, 01:24:13 PM »
The chart you refer to scales cleanly if you bump up the magnification/view, not so much the 'needle dimentions' graphic to the left but nothing new there anyway.

Yeah the PDF works way better,  I could even guess that L1 was the distance between top notch and where the taper reduction begins on the needle.  They use a degreed spec to determine the slope to the pointy end from there.  I think.  Lots of missing segments in the drawing, though.
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #16 on: June 16, 2005, 01:43:37 PM »
If your worried about Stock vs aftermarket needles, You can use a drill gauge to compare taper. Bob Wessner used my suggestion when comparing 750 needles. Interesting result, as the aftermarket was pretty different.

It seems a lot of people are under the (mistaken) impression that Keyster only makes one carb rebuild set for both the 550K and 550F. It appears that Keyster does in fact manufacture different sets with different needles for the CB550Ks vs. CB550Fs. That means there were actually different stock (KeiHin) needles as well, and our buddy Harry-the-Keyster-Man's note bears this out (see earlier in the thread).

I'm not convinced that the Keyster-woes so often reported are actually intrinsic to the quality of Keyster's needles. Someone complaining about the quality/performance of Keyster needles might not have been fully informed about differences between Keyster kits for the 550K vs. 550F.  That is, assuming they were told there are two different kits, let alone that the two kits have different needles and not just different Main Jets.

But ultimately, I'm not so much concerned about the presence of differences between stock vs. aftermarket (read here Keyster) needle taper, so much as whether those very differences might actually come in handy for ultra-fine tuning.

In other words:

Keyster Needle Size: #D274, which is intended to replicate the Stock KeiHin Needle #273004 for a CB550F (which came with a slightly narrower needle taper than the K for greater fuel flow) might actually provide too much fuel mid-range on a bike with a non-stock (less restrictive) air intake (pods).

In which case, Keyster's Needle #D26, the intended aftermarket replacement for KeiHin's Needle #272304 from the CB550K's carbs, might actually be a better choice (performance wise) despite the fact that it's not the intended aftermarket part for the CB550F.

Crap. I think I pulled something in my brain.

Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #17 on: June 17, 2005, 02:33:49 PM »
Anyone have these charts in an easier to read form?

For all you - ahem - older squinty-eyed folks.

Mikeshonda750F

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #18 on: June 17, 2005, 04:06:46 PM »
16012-390-004 Is the factory honda part number for the needles for a 1976 Honda CB550F SuperSport.

99202-601-0980 Is the factory honda part number for the main jet set. #98

99124-076-0380 is the factory honda number for the slow jets. #38

16013-329-004 is the part number for the float set.

These are straight from the honda parts fiche and are still avaliable from the stealer

Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #19 on: June 17, 2005, 10:30:02 PM »
Check it. All the related bits in one visual.

Offline TwoTired

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #20 on: June 17, 2005, 10:46:41 PM »
Nice, I like it.  But, I can't remember what I.M.S. stands for...

And, I wonder where float bowl fuel level fits into that chart?
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #21 on: June 18, 2005, 07:49:53 AM »
Nice, I like it.  But, I can't remember what I.M.S. stands for...

Idle Mixture Screw. CB500/550 carbs haven't got one.

Offline TwoTired

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #22 on: June 18, 2005, 10:29:50 AM »
Er, well, the 77-78 CB550K models have an I.M.S. but no I.A.S.

You just can't make many reliable predictions in world where all the constants turn into variables.
Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline nopivnick

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #23 on: June 18, 2005, 11:38:35 AM »
Stickler. I was going to make that little proviso, I was just feeling lazy.

Offline sophisticat

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Re: Compulsive Carburetor Questions Re: '76 CB550F
« Reply #24 on: August 03, 2011, 04:52:47 PM »
I have a 1976 cb550f. as far as i can tell all internal carb jets and needles were stock except at some point someone put 100 mains in. all the orings were shot so i ordered a set a carb rebuild kits, i in return was given the d26 needles in a kit for the 500/550. with all parts replaced and the jet needle on the same middle 3rd groove the bike is hitting a flat spot at 6500- 7000rpm. i am willing to move the needle 1 more down, richening the mix. however im not sure if this is because i have better seals with the orings, were before i may have been running richer from leaking around the oring, or because i have been sold the wrong kit for my bike. ill double check all the numbers when i get home