Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: nairb on May 20, 2026, 03:50:03 AM
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I have been trying to find if Honda ever said what the fuel height should be in the carbs of a CB550 K3.
Honda does say how far the float should dangle down .... 22mm I think.
But on my KZ750 twin I use a clear tube stuck in the bottom of the carb bowl and this gives the actual fuel height, As shown in the pic below.
[attach=1]
And Kawasaki says what the fuel level lines up with. All very helpful.
Does anybody know if honda ever did this for the 550 K3. I now need to check the float heights .... It would be interesting to try this with the carbs still on the bike.
Ta
Nairb
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No they didnt and i dont think 22 is correct, there are 2 different settings for K3 but cant remember what differences are, the K3 addendum should be in Ashs dropbox
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It's either 12 or 14mm, depending on model. See addendum CB550K3.
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It's either 12 or 14mm, depending on model. See addendum CB550K3.
I took the 22mm number from the "Honda CB500_CB550 Four Service Manual"........ See pic below
[attach=1]
But its not for the K3. I will check the addendum CB550K3.
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The 22mm figure is an upside down height from the carb body to the bottom of the float, , not the depth of petrol in the bowl.
That's my understanding.
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The 22mm figure is an upside down height from the carb body to the bottom of the float, , not the depth of petrol in the bowl.
That's my understanding.
Yes yr right. I guess if all the floats were of the correct (22mm). Then the fuel height would all be correct.....
Or stick a bit of clear tubing on the bottom of the carb and see what the fuel level actually is without having to take the carbs off (yet again). And take apart. I will try this to see if all 4 carbs are the same. Which is a start.
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So... it's about the float height in other bikes than the K3?
This method - given that it is a good idea to drain the floatbowls once a year - is still the simplest.
https://forums.sohc4.net/index.php/topic,185754.msg2151647.html#msg2151647
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Interesting link, not sure why the attachments for the photos will no work on my phone?
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Here they are
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So I tried the method given above and found all 4 carbs seem to hold 27 to 27.5 ml. Just one carb was more than the others by .4 ml.
Then I tried putting a clear plastic tubing on each of the carbs. 3 were almost the same with one nearly 4.5 mm less than the others.
Is this an issue??.. Dont know, but I will try to adjust it so it's the same as the other carbs.
The Kawasaki is very sensitive to fuel level heights which is why I wonder if the honda is also
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You got me confused... what carbs is this about: 069A? 627B? 022A? 087A? or PD carbs?
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So I tried the method given above and found all 4 carbs seem to hold 27 to 27.5 ml. Just one carb was more than the others by .4 ml.
Then I tried putting a clear plastic tubing on each of the carbs. 3 were almost the same with one nearly 4.5 mm less than the others.
Is this an issue??.. Dont know, but I will try to adjust it so it's the same as the other carbs.
The Kawasaki is very sensitive to fuel level heights which is why I wonder if the honda is also
Whilst it might be nice to have them all the same, the fuel volume will vary slightly due to the bowl moulding variations.
Do you mean a fuel height difference of 4.5 mm or .45 mm? The former is not good, it will need adjusting
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You got me confused... what carbs is this about: 069A? 627B? 022A? 087A? or PD carbs?
it says PD46A stamped on the side. The same ones that were on the bike when I bought it new.
I did have these all apart 2 or 3 years ago. It took a while to get them right back then. It starts and idles fine and has a smooth getaway. But starts to hesitate over 40+mph. A change of air filter (new one) made it far worse.
I did put on a new set of 4 into 4 exhausts from DSS a while ago.
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PD46 carbs have a float level of either 12,5 or 14,5mm. Consult Honda documents!
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14.5mm float level on PD46a
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So I seem to have the PD46AC......... which is different to the PD46AA
When I rebuilt the carbs2-3 years ago I used a spare float... it turns out it was a float from a pd46AA.
Which has a float level of 12.5 instead of 14.5. Here is a nice pic showing the two side by side
[attach=1]
One has "K" marked on(pd46aa) and the other not.
I can put the old one back in (no "K").
Might even explain why 3 carbs seemed to be ok and one not.
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In the past I've tried to find out which K3 carbs had the 14,5mm and which had 12,5mm float levels. Alas, I haven't found trustworthy sources. The one shown here is dubious, because it is by an American who thinks mentioning the 'year' is good enough. When in doubt, I'd opt for the 12,5mm level as 14,4 could result in a too lean mxture.
Can you shoot a picture of the front opening (exit so to speak) of your airfilter element? There have been differences there too: wider/smaller, but I don't know it is somehow related.
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Yes, the air filter. I purchased a new "Pattern" one that said it was for a cb550K3. Fitted it and the bike performance was worse. Quite a bit worse. So I put the old dirty one back in. The old one must have been purchased a few years ago.
Here is a pic of the two.
[attach=1]
Maybe there are different type of filter depending on the carb type.....pd46aa or pd46ac
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Makes me wonder what dimension the corresponding opening in the CHAMBER has. Have you checked?
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I have been trying to find if Honda ever said what the fuel height should be in the carbs of a CB550 K3.
Honda does say how far the float should dangle down .... 22mm I think.
But on my KZ750 twin I use a clear tube stuck in the bottom of the carb bowl and this gives the actual fuel height, As shown in the pic below.
(Attachment Link)
And Kawasaki says what the fuel level lines up with. All very helpful.
Does anybody know if honda ever did this for the 550 K3. I now need to check the float heights .... It would be interesting to try this with the carbs still on the bike.
Ta
Nairb
The fuel level with the clear tube should be about 3mm below the top of the bowl.