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Discussion Starter #1
Hi, I've searched the forum and can't really find an answer---
My bike is a '72 CL350 K4 with Keihan 722A (KB) Carbs, with round brass floats.
Does anyone know the correct float height (measured with the Carb Bodies held inverted)?

Seems it could be 19mm, 22mm or 26mm!

At present they are set on 22mm, it runs OK, if a bit flat, and needs hardly any choke to start on a cold morning--by UK standards!

Advice much appreciated.

Robin.
 

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I suspect you do not have the factory service manual. I know there are varied versions of your bike/carbs, there may be different specs as well. I've sent you a PM regarding the manual, likely one of the 350 experts will be along with more specific guidance.
 

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Discussion Starter #5
Thanks for that Boomer, I'm still wading through Tech Manuals, but I'm inclined to try your recommendation.

Robin.
 

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The Honda factory shop manual doesn't give the float heights or much else for the carbs. There's a Honda carb manual with all that in it. That said, it's 26mm, but mine runs much better with them set to 27.5mm.
 

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Discussion Starter #7 (Edited)
Hi, I've just come indoors out of the cold garage, where I had carefully set my Float Heights to 27mm, rebuilt the carbs on the bench and checked for fuel flow via my test tank--zilch! removed the float bowls which were clean and dry!!
It seems that at 27mm the float bowls impinge(good word?)on the floats and close the needle valves, preventing any fuel flow.
Tomorrow I'll revert to 22mm and see how that works.
I'm guessing that Honda and Keihin conspired to keep us awake nights by changing carb specs willy nilly!
Will report back.
Robin.
 

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Dogwheel either your method for setting the float height is incorrect or the parts you are using are wrong. You are too far off spec and going in a different direction than what the rest of us have found to work.

I have never had a set of these carbs not function at 26 mm and the last 4 sets I did have been set to 27mm without issue. Two rebuilds were done with OE Honda parts and two were done with aftermarket kits. All have no issues with allowing fuel into the float bowl and then stopping the fuel flow.
 

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Discussion Starter #9
Boomer, Would you please briefly outline the method you use to measure float height, I guess it's colder in your Alberta garage than mine in Worcestershire UK!
Robin.
 

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The bottom of the float should measure 26 mm (or 27.5 mm) from the float bowl mating surface when the float tang just touches the pin on the bottom of the float valve. Make sure to hold the carb vertical (or close to it) before tilting it, and make sure the float valve is seated all the way when you take the measurement.

carbs-17 jpg.jpg
 

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As above post by 83XLX. I also check both sides of the float as they often have a twist in them.

Make sure the needle valve spring is not gummed up and stuck in the up position. The pin/spring need to move freely.
 

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Something else to make sure of is installing the carbs level so the float level is horizontal. If the carbs are twisted a little in the mounts, the float level can be screwed up even if they are adjusted correctly on the work bench.
 

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Discussion Starter #13
Hi Boomer, Aha! That's very interesting, I had been advised to hold the carb inverted to measure, that means the little sprung pin is compressed by the weight of the float, the method shown in your picture now makes much more sense to me. Incidentally 27mm "my way" equates to 32mm your way, so I'll be using your way from now on.
Thanks very much,
Robin.
 

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Hi Boomer, Aha! That's very interesting, I had been advised to hold the carb inverted to measure, that means the little sprung pin is compressed by the weight of the float, the method shown in your picture now makes much more sense to me. Incidentally 27mm "my way" equates to 32mm your way, so I'll be using your way from now on.
Thanks very much,
Robin.
You're welcome...lol
 

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Discussion Starter #16
'morning, I thought I'd replied to this last night, but it seems to have disappeared.
I had been advised to measure float height with the carb inverted, this naturally means that the weight of the float compresses the little sprung pin on the needle valve, I'll try again using the method shown in your picture 83XLX, thanks for the info, I'll let you know how I it works out for me.
Robin.
 

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Discussion Starter #17
Hi, me yet again!

Float heights now set and checked carefully, it all makes sense, if I hold the carb vertical, at 90 degrees, as in 83XLX photo, then it measures 27mm.
---------------------------------------------------------------------- if I hold the carb horizontal and inverted at 180 degrees, then it measures 22mm.

Thanks again for all the help.
Robin.
 

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Discussion Starter #18
Hi Guys,
I've set the float heights as advised, checked all the carb adjustments and fitted new(expensive) air filters. Wow! What a difference, quite a few sleeping horses are now "woke".
The old air cleaners did not look too bad, but I guess 11,000 miles in Nebraska might have sucked up some fine dust, I might try stripping out the paper from those old filters and converting them to washable foam.
I've now got another query about this bike, but not under this section.
Thanks again,
Robin.
 

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Try blowing the dirt out of the old old air cleaners by using compressed air from the inside and tapping them on a hard surface. That's what Honda recommended doing to clean them, and you may end up with a decent pair of replacements (or a pair you can sell) instead of destroying them.
 
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