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Author Topic: CB350F float height?  (Read 5264 times)

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Offline lhemrick

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CB350F float height?
« on: May 22, 2018, 08:08:36 AM »
The site won't let me search so I'm forced to ask. 1972 Honda CB350F. My Clymer manual says they should be 21mm. I see the photos have brass floats mine are Composite. There is no way to set these floats to 21mm. I usually use the clear tube method to set the fuel level anyway but I'm looking for a good starting point. Can anyone assist with some info?

Thanks!
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Offline kslrr

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Re: CB350F float height?
« Reply #1 on: May 22, 2018, 08:18:45 AM »
The carbs on my '72 CB350F have then same composite floats and I am able to adjust the float height by bending the float valve tang as shown.  Do your floats not have a bras tang, that is part of the frame that holds the floats, that can be bent for adjustment?
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Offline lhemrick

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Re: CB350F float height?
« Reply #2 on: May 22, 2018, 08:35:42 AM »
Yes they have the tang. When I said they can't be set 21mm is that you can't bend the tang far enough to get them down to 21mm.
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Offline carnivorous chicken

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Re: CB350F float height?
« Reply #3 on: May 22, 2018, 09:21:42 AM »
350Fs don't have brass floats, so you've got the right ones. Are you sure they're not mounted upside down? I've seen it... But yes, you should be able to adjust to the right height with the tang, although float heights usually don't change so it's somewhat rare to have to adjust. And as you state, always good to double check with the clear tube method.
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Offline lhemrick

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Re: CB350F float height?
« Reply #4 on: May 22, 2018, 10:21:01 AM »
Its not possible to put these in upside down because of the spring clip that holds the main jet in.
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Offline carnivorous chicken

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Re: CB350F float height?
« Reply #5 on: May 22, 2018, 10:25:55 AM »
I'm assuming if you haven't set the float height, you haven't put the bowls back on, which means you haven't got the spring clips in place...
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Offline lhemrick

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Re: CB350F float height?
« Reply #6 on: May 22, 2018, 10:51:05 AM »
You are correct. No bowls or clips at this point.
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Offline flybox1

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Re: CB350F float height?
« Reply #7 on: May 22, 2018, 12:37:16 PM »
IMO, Clymer is inaccurate for the 350F float height. 
Clear tube method (-3mm) resulted in floats closer to 24mm.
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Offline Bodi

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Re: CB350F float height?
« Reply #8 on: May 22, 2018, 12:58:48 PM »
21mm is the correct measured float height. Check what you want with a clear tube, I don't see the point... are you incapable of adjusting by measurement? Obviously 21mm measured won't equal 21mm actual fuel level: see Archimedes Principle.
The measurement is from the flat bottom of the float to the flat gasket surface on the body. The float bottom should be almost perfectly level at 21mm but I measure close to the center line anyway.
You can indeed put the floats in upside down. I don't see what the jet retainer has to do with that. To me they look correct with the rounded bits facing out, but naturally this is wrong.
In many 350/400 carbs I have easily adjusted the tang - very little bending ever needed, actually - to get 21mm.  If you need to bend them very much or they won't bend enough, something is very wrong like maybe strange float valves have been used. (or the floats are inverted)
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Offline lhemrick

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Re: CB350F float height?
« Reply #9 on: May 22, 2018, 02:42:12 PM »
These floats can not be installed upside down. Your sarcastic reply about not being able to read a ruler is not wanted or needed. Thanks anyway Richard!
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Offline Bodi

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Re: CB350F float height?
« Reply #10 on: May 22, 2018, 03:41:32 PM »
That was directed at folks recommending adjusting with a clear tube, not at you. I see what you mean about the floats but I have seen them inverted, must have been other carbs, or taken some severe abuse to get them in.
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Offline kslrr

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Re: CB350F float height?
« Reply #11 on: May 22, 2018, 03:55:04 PM »
Two more questions: 1) is there a possibility that someone else had worked on these carbs before you?  2) is it that you cannot get it down to 21mm or up to 21mm?
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        1981 CB650 engine
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Then 1972 CL175
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Offline lhemrick

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Re: CB350F float height?
« Reply #12 on: May 22, 2018, 04:20:10 PM »
I've rebuilt them myself about ten years ago. Yes for some reason I can't get the tang bent far enough back to get lowest part off the float to 21mm from the base.  I've set them to 24mm and tomorrow I will put some fuel to them on the bench and see how high the bowls fill.
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Don't give up; Rust is only Temporary!
77 Honda CB750
70 Honda CB350 twin
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72 Honda CB350 Four
72 Honda CB175
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81 KZ750H2
82 KZ750M1 CSR
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Offline carnivorous chicken

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Re: CB350F float height?
« Reply #13 on: May 22, 2018, 04:45:03 PM »
Quote from: lhemrick on May 22, 2018, 02:42:12 PM
These floats can not be installed upside down. Your sarcastic reply about not being able to read a ruler is not wanted or needed. Thanks anyway Richard!

Uh... one of those floats is installed upside down. Just look at the photo -- one of these things is not like the other. Do you see how on the left the flat side is facing down, and on the right the round side is facing down?

You can lead a horse to water... but at least now you know it's an easy fix.
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Offline kslrr

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Re: CB350F float height?
« Reply #14 on: May 22, 2018, 04:46:23 PM »
I'm sure you are doing it right.  Carbs upside down, floats resting on the sprung pin of the float valve.  It could be a sign of incorrect float valves and/or float valve seats.  Or the seats not fully pressed in.
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Now  1972 CB350FX (experimental v2.0)
        1981 CB650c Custom with '79 engine (wifes)
        1981 CB650 engine
        2004 HD XL883C Custom
        1977 Yamaha XS750D (in progress)
Then 1972 CL175
        1964 Yamaha YGS-1T
No ride is a Bad ride

Offline lhemrick

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Re: CB350F float height?
« Reply #15 on: May 22, 2018, 05:13:56 PM »
First that photo was to show that they can't be installed upside down. Second I do have new aftermarket needles and am wondering the same things about them.
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Don't give up; Rust is only Temporary!
77 Honda CB750
70 Honda CB350 twin
71 Honda CB350 twin
72 Honda CB350 Four
72 Honda CB175
81 KZ550C2
81 KZ750H2
82 KZ750M1 CSR
84 ZN700 Shaft

Offline Robbo

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Re: CB350F float height?
« Reply #16 on: May 22, 2018, 05:29:38 PM »
21mm is the correct height

Measure the carbs on an angle as shown in the attached photo with the tang just lightly touching the valve pin...but not depressing the spring.




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