Author Topic: The actual fuel hight in these 550 K3 Carbs  (Read 9471 times)

Offline nairb

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The actual fuel hight in these 550 K3 Carbs
« on: May 20, 2026, 03:50:03 AM »
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.

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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
cb550k3, cl450k5, re5m, xs650xs2, mt500, kettle, gt550 x2, gt380 Kz750 twin, cb360K0 and an old working bicycle

Offline Bryanj

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #1 on: May 20, 2026, 05:58:14 AM »
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

Offline deltarider

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #2 on: May 20, 2026, 07:52:31 AM »
It's either 12 or 14mm, depending on model. See addendum CB550K3.

Offline nairb

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #3 on: May 20, 2026, 01:37:59 PM »
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

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But its not for the K3.  I will check the addendum CB550K3.
cb550k3, cl450k5, re5m, xs650xs2, mt500, kettle, gt550 x2, gt380 Kz750 twin, cb360K0 and an old working bicycle

Offline McCabe-Thiele (Ted)

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #4 on: May 20, 2026, 02:47:07 PM »
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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Offline nairb

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #5 on: May 20, 2026, 08:16:13 PM »
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.
cb550k3, cl450k5, re5m, xs650xs2, mt500, kettle, gt550 x2, gt380 Kz750 twin, cb360K0 and an old working bicycle

Offline deltarider

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #6 on: May 21, 2026, 06:50:04 AM »
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

Offline McCabe-Thiele (Ted)

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #7 on: May 21, 2026, 09:13:03 AM »
Interesting link, not sure why the attachments for the photos will no work on my phone?
Honda CB400NA Superdream (current money puddle)
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https://www.sohc.co.uk/index.php/topic,28541.0.html
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Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html
This is a neat 500 restoration in the USA.
http://forums.sohc4.net/index.php/topic,151576.msg1731556.html#msg1731556

Offline deltarider

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #8 on: May 21, 2026, 03:33:23 PM »
Here they are

Offline nairb

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #9 on: May 22, 2026, 02:38:39 AM »
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
cb550k3, cl450k5, re5m, xs650xs2, mt500, kettle, gt550 x2, gt380 Kz750 twin, cb360K0 and an old working bicycle

Offline deltarider

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #10 on: May 22, 2026, 06:47:07 AM »
You got me confused... what carbs is this about: 069A? 627B? 022A? 087A? or PD carbs?

Offline McCabe-Thiele (Ted)

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #11 on: May 22, 2026, 08:29:26 AM »
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


« Last Edit: May 22, 2026, 01:13:31 PM by McCabe-Thiele (Ted) »
Honda CB400NA Superdream (current money puddle)
Honda CB500 K1 (second money pit)
https://www.sohc.co.uk/index.php/topic,28541.0.html
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html
This is a neat 500 restoration in the USA.
http://forums.sohc4.net/index.php/topic,151576.msg1731556.html#msg1731556

Offline nairb

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #12 on: May 23, 2026, 03:39:47 AM »
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. 
cb550k3, cl450k5, re5m, xs650xs2, mt500, kettle, gt550 x2, gt380 Kz750 twin, cb360K0 and an old working bicycle

Offline deltarider

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #13 on: May 23, 2026, 06:59:45 AM »
PD46 carbs have a float level of either 12,5 or 14,5mm. Consult Honda documents!
« Last Edit: May 26, 2026, 07:58:47 AM by deltarider »

Offline Nurse Julie

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Re: The actual fuel hight in these 550 K3 Carbs
« Reply #14 on: May 23, 2026, 07:40:10 AM »
14.5mm float level on PD46a
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