Topic: carb identification

[hymodyne]

hi,
recently i posted some questions about carb kits that didn't match my carbs. It has since been discovered that my carbs are not cb500 but cb550''s  currently in use on a cb500/4K1. should I take this to explain the rich running nature of the engine when I had the carbs set as if they were 500's?

If they are 550's, with air pods and a 4-1 exaust, my thought was to go with the middle jet needle setting, assuming that the middle, while normal for a 550, would be too rich for a 500, but hopefully just right for one outfitted with aftermarket exaust and breathers.
 
any suggestions would be helpful. I'm aware I have a few trial and error setting sessions ahead of me.


the numbers stamped onto the main carb bodies is 627B.
Can someone please verify what motorcycle make and year these carbs are supposed to go on? I've seen float heights vary between 14mm and 30mm for carbs on cb500's and 550's.

a proper ID will go a long way towards setting these things correctly.

many thanks,

hym

[TwoTired]

627B= CB500 71-73  (Float height 22mm, from Honda Shop Manual)
022A=CB550K 74-76
069A=CB550F 75-77
? =CB550K 77-78

[SteveD CB500F]

My '77 550K3 has PD46A stamped on the side.

[Warlock]

Greets,

CB550K-77: X46A carbs
float level: 14.5mm
mains: #90
slows: #38

CB550K-78: PD46C carbs
float level: 12.5mm
mains: #90
slows: #42

[TwoTired]

Ok off my 78 CB550K   -  PD46CAPK

Spare set from ?  - PD46CAPF

Both these numbers are followed by a japanese character I can't print here.  But, I don't think they are the same.

The Honda shop manual chapter 19 supplement to the CB500K3/CB550K3 (77), has a carb setting table.  Conveniently (not) they don't list any numbers that are actually on the carb.  But, the slow jet differences listed by Warlock show in columns labeled  CB500K3 and CB550K3.  Along with air jet and needle type/groove placement differences.   The float heights are the same 14.5mm for both.

How can we resolve these discrepancies?  Is there truely a difference between 77 and 78 K3 Cb550s?  And, why would this be?  The pipes, air filter, and engine are the same between these years, aren't they?  Can you name your source documentation?

[Warlock]

Honda Motorcycle Service Specifications for all 1959-1980 US Models....

[TwoTired]

Cool,

Any idea where I could find or look for a copy of this?

Cheers,

[Warlock]

Greets,

Since most of my technical/training manuals were acquired from a dealership back in the day, I assume they are no longer in print. You could try Ebay or a web search engine to locate a copy. Attached is a scan of the cover if it will help you....

 

[Jeremy]

Carbs on the my 77 cb550k pd46cape
Replacement set pd46aapdi, are these ok, anyone know of any other differences. Hey warlock can you post a scan of carb specs and float heights?

[Warlock]

Greets,

For your viewing pleasure....

[gearhead]

It looks like I found the right place.

Hey Warlock!  You are the man I need to help me through this dilemma.
I have a 76' 750r engine on a custom frame I fabd(chopper style) and I am experiencing carburator hell.
Right now I am running 086A  ANI I found at a junkyard and went through.   This block came with 7A JB model    and I also have 064A ANB   
all of these are in their respective harnesses and synchros.  Can you by chance help me with tuning these?  I had the engine align bored .040 and has large hedders.  I seem to be running too rich no matter what I do.  I saw the spec chart you posted.  could you help a fellow Honda out?
Greg

[bryanj]

Warlock, on the back cover of that book, in small print, may be a set of numbers/letters that would be the part number to try and order another

[Warlock]

Greets,

Bryanj- The publication number: CRTC S0544

Gearhead- When you rebuilt the carbs, did you happen to note the main/slow jet sizes that were installed? Also the jet needle settings? You will need this information before you can decide on a course of action. You must remember that carb tuning is a trial and error process and a baseline is needed for reference. We all wish there was a formula for determining jet sizes when making modifications. It would make life simpler, but we live in the real world.

Check the simple things first. Float height in particular, as this is a critical setting. It should be 26mm. The standard slow jet for the 086A should be a #40. Standard main is a #105. Standard needle position should be 4th groove from the top. If different jets are installed, compare them to the standard sizes, then decide if they need to be changed to a different size. Also check the needle setting. When tuning carbs, it is wise to document everything that is done and the resulting effects. Be objective. If you have not read the FAQs on carburetion, it might be to your benefit. Understanding how carburetion works can make it easier for you.

Also, I assume you have checked all four cylinders for a rich condition and it is not just a question of one or two carbs loading up. Verify this with whatever procedure you have chosen to ascertain that the rich condition is affecting all cylinders. If it is not, you will need to examine more closely only the carb(s) in question. Be as thorough as possible when troubleshooting. Do not guess...

[gearhead]

 Thanks Warlock
Since I put 900 heads ported on this low end I assumed that it would require a bit more fuel.  These carbs were set at 30mm which actually made a bit of fuel drip from the overflow at a stoplight. at 26mm It would suck those babies dry if I get on it hard(which it seems to do at a feather touch)  The slow jets are 44  and the main is 115  I also have the needle at 5th  from top.  Thank you for helping me establish a stock base to start from.  Like you said- no guesswork.  Maybe I should invest in some newer models??  maybe 38mm carbs or something?
what do you think?
Kudos,
Greg

ridered

[Warlock]

Greets Gearhead,

If you feel ambitious, you could change out the carbs. But, regardless of the type of carb you install, re-jetting will probably still need to be done. Also consider, when unsure of the breathing ability of the engine, it is better to have the engine under-carbureted in terms of air flow. An over-carbureted engine will perform less efficiently (especially at idle) and be more difficult to dial-in than an under-carbed one. If you are certain of the intake air flow characteristics of your engine, then use your best judgement (plus any other real world advice available to you) in choosing carbs with the appropriate throat size. With a little patience, I am certain you will be able to dial in the jetting (and resolve your rich condition) on whatever carbs you may decide to use. If you have access to an exhaust gas analyzer, it could also make your task much easier. Happy carbureting......