Topic: cb500 carbs on a cb550

[Spikeybike]

ok so my simple carb rebuild just got interesting
 
i have a 75 CB550F , while tearing down the carbs i noticed the casting marks are 022A which is the 71-73 CB500 . now i know these will work with proper jetting but i'm not sure where to set the float height or where to set the needle position

the standard float height for the 500 is 22mm and i dont know what the standard needle position is

any ideas ?

[TwoTired]

The proper carbs for a 75 CB550F are stamped 069A.
022A carbs are normally found on a CB550K with the 4 into 4 exhaust.
CB500s usually have 627A or B as the set up stamping.

The setup stamping refers to internal parts such as jets, slide needles, emuslion tubes, etc.  Many of which are defined in a FAQ chart in this forum.

The set up parts inside the carbs are used to match breathing characteristics of the engine with the stock air filter and exhaust system.  If these change stock settings do, too.

Didn't do much of a search did you?  This has been discussed many times before.

Cheers,

[Spikeybike]

ok ok i'll search more ... i did look, but not that hard . (damn)

and i thought they were cb500's from this link http://www.motorcycleproject.com/motorcycle/text/specs.html

[TwoTired]

Yes, that is Mike Nixon's site.  It's a good site.  But, I'm afraid his specs are wrong in that area.  I sent him a correction and the rationale, for which he thanked me, and then ignored the input.
Se la vie

His chart doesn't have any data for the 087A (late 76K models) and 627A or b setups at all.  Note he has no carb setup numbers for the 74-76 Ks?

My collection of bikes and findings on many others, supports my data.  Even the Honda shop manual has a misprit regarding the 022a Carbs in the F model supplement.

Believe what you like...
Cheers,

[oldfart]

Yes, that is Mike Nixon's site.  It's a good site.  But, I'm afraid his specs are wrong in that area.  I sent him a correction and the rationale, for which he thanked me, and then ignored the input.
Se la vie

His chart doesn't have any data for the 087A (late 76K models) and 627A or b setups at all.  Note he has no carb setup numbers for the 74-76 Ks?

My collection of bikes and findings on many others, supports my data.  Even the Honda shop manual has a misprit regarding the 022a Carbs in the F model supplement.

Believe what you like...
Cheers,

Lloyd -- Sorry, old friend, if it seems I ignored you.  I didn't mean to.  I just hardly every find time to update that site.  :-)  Tell me again what I can do to make it more accurate and I will try to get it fixed.  Thanks!

[Kevin400F]

Below is a scan of several pages from the Honda "Motorcycle Service Specifications Manual", circa 1977.  Although it doesn't include reference to all the carb model numbers, it does list the jet sizes and float settings.  My stock '76 550K does indeed have the 087A carbs, as Lloyd mentions.

[MotoRico]

If I am interpretting that correctly, between the CB500 and the CB550K it looks like they went with a smaller idle jet and only backed the idle adustment screw 1 and a half turns instead of 2.  So they let in less fuel with a smaller jet and less air by only backing the screw out 1 and half turns instead of 2 full turns.

If I remember correctly, the idle adjustment is to control the amount of air, not the amount of fuel.  I've been reading up on carburetors so any feed back would be great.

[TwoTired]

So they let in less fuel with a smaller jet and less air by only backing the screw out 1 and half turns instead of 2 full turns.

Probably not.  The different settings between the 500 and 550 are far more likely due to the displacement change.  A larger displacement engine draws more air volume and, therefore, the depth of the partial vacuum presented to the jets is deeper when using the same carb and air filter type.  The partial vacuum is what draws more fuel through them.  The reduction in jet size and air screw adjustment (as well as changes to slide needles and emuslion tube holes) is to compensate for the draw characteristics of the engine.

From information I've been able to glean over the years, the carb setup stamping is as follows:
627A - 1971 CB500
627B - 1972 and 1973 CB500
022A - 1974 and 1975 CB550K
087A - 1976 CB550K
069A - 1975 through 1977 CB550F
X46A - 1977 CB550K  (K3)
PD 46A - 1978 CB550  (K3)
??  - CB500  (K3)
??  - European model CB550 (K1?) with air restrictor horn.

It should be noted that, except for the last two)  these are for American models.  I've had discussions with some European members who have machines with an air restrictor on the intake filter box.  These have yet another set up stamping on the carbs, with smaller main jets and, I'm fairly confident, other internal parts differences.  It's not likely I'll ever encounter, or measure  these carbs.


I've compiled a list of known differences and the chart can be found in the FAQ.
I've never actually seen the 627A stamped carbs.  But, I've been assured they do exist by forum member's claims of visual verification.
I don't know the internal differences, however.

I currently have examples of the rest, and plan to measure and collect data regarding the internal pieces to note the differences. Unfortunately, several life issues have interceded, and I don't yet have that data, beyond what is currently placed in the FAQ's chart.

Cheers,

[Beans]

On the carbs where can I find out what carbs are on my bike?   I know it should be a 069A from this topic but where are they stamped on the carbs?

[TwoTired]

Stamped on each carb body mount flange, top right, for the early carb style (not PD).

[Beans]

Stamped on each carb body mount flange, top right, for the early carb style (not PD).

ok cool.

[bikes4dan]

Just a quick question, I just picked up a 73 CB500 that needs a little carb work, can anyone tell me how far to back out the adj screws?

[TwoTired]

You mean the Idle Air bleed screws?  They are left at factory setting, (listed on the Chart within the FAQ) unless the bike has been changed from stock configuration.