Author Topic: Carb needle settings.  (Read 1389 times)

Offline Brian.

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Carb needle settings.
« on: July 29, 2020, 08:51:15 AM »
Good morning all,

I'd like to ask for some help please.  I've done a few searches on here, plus on the net in general, and I can't find it.

I've been doing some work on my CB550K1.  When I bought it the carb needles were in different grooves  :-X
and I couldn't find an answer then, so I put them in the middle groove, purely because every other bike I've had cause to check needles, that's where they were.

But I'm sure I've since seen that they should be in the second one down? 

I'd like to know 100% before I balance my carbs.  It has the standard jetting, standard airbox and DSS four pipes.

Thank you  :)

Brian.

Offline Brian.

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Re: Carb needle settings.
« Reply #1 on: July 29, 2020, 10:06:14 AM »
Brian,
             Have you had a look in the Aladdin's cave section on this forum.
Loads of info and manuals.  ;D
Yes I did, thank you Paul, and I couldn't find it on there either.  I agree, it's an excellent resource, I found it to be very helpful when I was doing my head and base gasket replacement recently.

I've also downloaded the 550 manual and parts book from Aladdin's cave too.  I also checked in the 500 manual because the ever-helpful Bryan J told me that sometimes when Honda omit information from, for example, the 550 manual it's because the 550 manual is an update of the previous (500/4) manual; so I looked on there and I couldn't find it there either.  Air screw turns out etc, all there, but not the needle clip position.

It's probably staring me in the face somewhere, but despite my efforts I could not find it, hence asking the good people on here because I'd like to be out on it tomorrow, all done and dusted!

Thank you for replying, by the way.

Brian.
« Last Edit: July 29, 2020, 10:17:08 AM by Brian. »

Offline paul G

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Re: Carb needle settings.
« Reply #2 on: July 29, 2020, 10:16:30 AM »
Honda CB400 4
Honda CB550 K3 (sold)
Honda CB750 UK K1
Kawasaki Z650 C2
Kawasaki Z650 cafe racer (Sold)
Honda CD175 sloper

Offline Brian.

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Re: Carb needle settings.
« Reply #3 on: July 29, 2020, 10:20:32 AM »

Online Bryanj

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Re: Carb needle settings.
« Reply #4 on: July 29, 2020, 10:24:58 AM »
Only mention i can find is page 178 which is the K3 supplement and refers to PD carbs and its 3rd groove for 550 but 2nd for 500(K3 500 never came to UK  officially).

There is also a carb setting table on page 165 (550F-A) which i find confusing.

Offline Brian.

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Re: Carb needle settings.
« Reply #5 on: July 29, 2020, 10:55:37 AM »
Only mention i can find is page 178 which is the K3 supplement and refers to PD carbs and its 3rd groove for 550 but 2nd for 500(K3 500 never came to UK  officially).

There is also a carb setting table on page 165 (550F-A) which i find confusing.

Thank you Bryan; yes I saw that too from what I've read on here the PD carbs on the K3 are not like mine so I disregarded it.

Brian.

Offline paul G

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Re: Carb needle settings.
« Reply #6 on: July 29, 2020, 10:59:13 AM »
Found this topic but it may well be worth contacting Gerben on this forum to confirm.

http://www.sohc.co.uk/index.php?topic=19413.0
Honda CB400 4
Honda CB550 K3 (sold)
Honda CB750 UK K1
Kawasaki Z650 C2
Kawasaki Z650 cafe racer (Sold)
Honda CD175 sloper

Offline deltarider

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Re: Carb needle settings.
« Reply #7 on: July 29, 2020, 11:14:35 AM »
There is also a carb setting table on page 165 (550F-A) which i find confusing.
Rightly so. The Shop Manual Honda CB500 - CB550 clearly has an error on that page 165. https://www.classiccycles.org/media//DIR_1653304/DIR_1653404/DIR_1653507/ecc6759db0a214d5ffff8824ffffe41e.pdf
Over the left column in the Carburetor setting table you should read CB550 and not CB500.
Not only would it be unlogic to compare CB500 and CB550 carbs on that page - and perfectly logic to compare CB550K carbs to CB550F carbs - also... no CB500 models ever had the 022A carbs.
Now to the question Brian has posted. The standard position seems to have been 4th from top. Source is an America Honda booklet with carb settings for several Honda's.
BTW, based on all the info I was able to find, I have compiled an overview myself. I have limited my search for the oldstyle carbs like you have.

Offline Brian.

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Re: Carb needle settings.
« Reply #8 on: July 29, 2020, 11:00:39 PM »

Now to the question Brian has posted. The standard position seems to have been 4th from top. Source is an America Honda booklet with carb settings for several Honda's.
BTW, based on all the info I was able to find, I have compiled an overview myself. I have limited my search for the oldstyle carbs like you have.
Thank you Deltarider.  I'm surprised it's fourth from the top!  This would then raise the needle.  That will make it run richer than first, second or third groove, won't it?  I would have thought that with US awareness of emissions in the 1970s that it would be weaker if anything.  Maybe I'm wrong about that.

Thank you very much for replying.

Regards, Brian.

Offline deltarider

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Re: Carb needle settings.
« Reply #9 on: July 30, 2020, 07:29:11 AM »
Brian, forsaid booklet is an edition (1977) by American Honda Motor Co., Inc. But... also p.165 in the Shop Manual Honda CB500 - CB550 gives us some indication. Have a close look at both columns, if you like, where the carbs are further specified. In the third line we read in the CB500 (which should be CB550(K)) column: '4 grooves' and in the CB550F-A column '2 grooves'. Read so, this is incorrect, because the CB550(K) actually had 5 grooves and the CB550F models had 4. Now what if this has been a clumsy translation by some Japanese Honda clerk who has struggled with English? I mean if we read: 4th groove and 2nd groove respectively, the information is correct.
Now a sidestep to the CB500. That same booklet specifies for the US CB500 an airscrew opening of 2 turns out and the needle in 4th position, where in Europe the CB500 had 1 turn out and the needle in 3rd position.
My explanation is as follows. Having seen the smog above Los Angeles in the early 70s with my own eyes, it was clear, authorities had to respond to this. I seem to have a vague recollection that they have started by reducing the harmful emissions at idle. As you know, the early CB550 models with oldstyle carbs have not been exported to Europe. However, if they had been imported here, we can't rule out the carb setting would have been: one turn out and needles in 3rd position, analogue to the choices they had made with the CB500 before. So it's your choice. :D
« Last Edit: July 30, 2020, 07:43:51 PM by deltarider »

Online K2-K6

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Re: Carb needle settings.
« Reply #10 on: July 30, 2020, 08:16:01 AM »
Deltarider,  it looks like that information adds as much confusion as it does clarity to the question.  There's too many provisions to make changes to come out with any degree of certainty.

The adjustment for both needles and airscrew are effectively a response to local average barometric pressures (generally oxygen content) and designed into most carburettor to facilitate this,  else you'd be forced to swap jets to fit the engine within it's market location. 

The overall jet size makes the emission level as designed ( essentially an absolute unless changed) with adjustment made within that to facilitate local variance of air component.  If they've done this thoroughly the adjustment will usually sit at mid range with specific advice to differ IF experience like flat spots were obvious. I don't feel they are ever given as absolutes though,  merely advised and qualified starting points.

The airscrews particularly don't change the total flow of an idle circuit,  just the gradient of change and it's starting volume at lowest rpm.  Maximum flow is fixed as that of the jet bore,  but the position of the airscrew alters how much of that flow is delivered at the lowest venturi flow. 
Airscrew further out just drops the "floor" % to start,  but it'll still flow the same as it gets to peak flow of idle circuit wherever you place the screw.
Airscrew fully in,  the idle jet will just flow at maximum as soon as you start the engine with no noticeable gradient. 

Given that it's not clear within generally available advice,  it's realistic to start the needles in the middle position I feel.

 

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