Author Topic: CB750 K7 float height?  (Read 4671 times)

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Offline mudhustler

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CB750 K7 float height?
« on: September 17, 2011, 03:49:37 PM »
I posted this question on my build thread, http://forums.sohc4.net/index.php?topic=89923.0, but also wanted to ask here.

Can anyone tell me the proper point I should be measuring from to set the float height on my K7 carbs?  ???  The bottoms of the floats are flat, as opposed to the rounded shape of the floats on earlier models, and measuring from different points along that horizontal plane yields different results for the same measurement of 12.5 mm.  See the picture below.



12.5 mm is the height given by the Honda shop manual for this bike.

When the float is level, the measurement is approximately 14.5 mm from the seating surface of the carb body to the bottom of the float.
If it ain't broke, don't fix it!  -my dad

Offline Terry in Australia

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Re: CB750 K7 float height?
« Reply #1 on: September 17, 2011, 04:01:21 PM »
G'Day Mate, turn your carbs upside down and take the measurement from the highest point on the float to the adjacent mounting flange on the carb body. Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

Offline mudhustler

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Re: CB750 K7 float height?
« Reply #2 on: September 17, 2011, 04:32:22 PM »
Terry, thanks for the reply!  A little early there isn't it?  Is this what you meant?

If it ain't broke, don't fix it!  -my dad

Offline Terry in Australia

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Re: CB750 K7 float height?
« Reply #3 on: September 17, 2011, 05:03:08 PM »
Yep, that's it mate, and it's around 10am as I type this. How do you do those neat graphics on your pics? Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

Offline mudhustler

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Re: CB750 K7 float height?
« Reply #4 on: September 17, 2011, 05:09:42 PM »
Great!  Thanks so much, Terry!  I guess it's not as early there as I thought, but it is tomorrow!

I use a free, open-source program called GIMP to edit and add graphics to my photos. 
Think of it as a free equivalent to the $500+ Adobe Photoshop!  It comes in very handy and is pretty easy to learn with all the tutorials and forums on the web.  You can check it out (and download it, if you want to try it out) at http://www.gimp.org/

Thanks again for the help! :)
If it ain't broke, don't fix it!  -my dad

Offline Terry in Australia

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Re: CB750 K7 float height?
« Reply #5 on: September 17, 2011, 05:16:57 PM »
No worries mate, and thanks for the tip! Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

Offline BobbyR

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Re: CB750 K7 float height?
« Reply #6 on: September 17, 2011, 05:21:59 PM »
As a quick check you can attach a piece of clear tubing to the float bowl drain and hold it next to the carb body. Since fluids seek their own level the level in the tube and the float bowl should be equal. The gas level in the bowl should be just below the gasket surface.
Terry knows his stuff, you have all the answers you need on this problem.
Dedicated to Sgt. Howard Bruckner 1950 - 1969. KIA LONG KHANH.

But we were boys, and boys will be boys, and so they will. To us, everything was dangerous, but what of that? Had we not been made to live forever?

Offline mudhustler

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Re: CB750 K7 float height?
« Reply #7 on: September 17, 2011, 05:35:47 PM »
When I set the float height as directed above, the float tang is touching the spring-loaded needle on the float valve.  Is this correct?

If it ain't broke, don't fix it!  -my dad

Offline Terry in Australia

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Re: CB750 K7 float height?
« Reply #8 on: September 17, 2011, 05:39:49 PM »
Yeah mate, the float position controls the opening and closing of the float valve, so the tang needs to be in contact with it. Cheers, Terry. ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

Offline mudhustler

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Re: CB750 K7 float height?
« Reply #9 on: September 17, 2011, 06:53:31 PM »
Cool.  I think I'm finally starting to understand how the mechanism works.  Thanks again!
If it ain't broke, don't fix it!  -my dad

Offline Spanner 1

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Re: CB750 K7 float height?
« Reply #10 on: September 17, 2011, 08:49:24 PM »
Mud and Terry.... c'mon guys floats upside down is wrong !!..... can't have the weight of the floats compressing the valve needle spring  :(... carbs need to be held sideways with the float pivot pins vertical and the float tab 'just' touching the ( fully seated ) float valve..........

Side Note; Hey Terry we kicked yer asses in the Rugger today ( IRL )... great game and first time we beat yis in 9 games ? ( Rugby World Cup )....
If your sure it's a carb problem; it's ignition,
If your sure it's an ignition problem; it's carbs....

Offline mudhustler

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Re: CB750 K7 float height?
« Reply #11 on: September 17, 2011, 09:57:16 PM »
Spanner, thanks for getting in on the conversation. 

The way you're describing it is exactly how I ended up setting the floats, with the float valve fully seated and the tang on the float assembly just barely touching the spring-loaded pin in the center of the valve.  The way Terry described worked fine for me, as the spring in the valve is strong enough to hold up the float assembly without being compressed.  Also, setting it this way made the measurement from the bottom of the float's end farthest from the pivot to the seating surface on the carb body just about 12.5 mm, as the shop manual said it should be. ;D

You're post confirms for me that I ended up doing it right.  Thanks again!

One thing that I noticed is that if the tangs are not set at the same heights in relation to their respective floats then all bets are off.  The floats could all be set to the same heights but the valves could all be in different states of closure!
If it ain't broke, don't fix it!  -my dad

Offline dtmmil

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Re: CB750 K7 float height?
« Reply #12 on: September 18, 2011, 12:09:39 PM »

Offline mudhustler

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Re: CB750 K7 float height?
« Reply #13 on: September 18, 2011, 12:18:49 PM »
thanks dtmmil!
If it ain't broke, don't fix it!  -my dad

Offline lucky

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Re: CB750 K7 float height?
« Reply #14 on: September 18, 2011, 03:57:24 PM »
All of is is a waste of time if the float needles are not brand new.

Offline BobbyR

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Re: CB750 K7 float height?
« Reply #15 on: September 18, 2011, 04:05:32 PM »
Not much different than the mechanism in a toilet tank. Gas on, gas off. Principle is simple, getting it right is a #$%*.
Dedicated to Sgt. Howard Bruckner 1950 - 1969. KIA LONG KHANH.

But we were boys, and boys will be boys, and so they will. To us, everything was dangerous, but what of that? Had we not been made to live forever?

Offline Terry in Australia

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Re: CB750 K7 float height?
« Reply #16 on: September 18, 2011, 04:10:53 PM »
Ha ha, Bobby said "Toilet" and "Gas" in the same sentence! ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

Offline Terry in Australia

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Re: CB750 K7 float height?
« Reply #17 on: September 18, 2011, 04:16:23 PM »
Mud and Terry.... c'mon guys floats upside down is wrong !!..... can't have the weight of the floats compressing the valve needle spring  :(... carbs need to be held sideways with the float pivot pins vertical and the float tab 'just' touching the ( fully seated ) float valve..........

Side Note; Hey Terry we kicked yer asses in the Rugger today ( IRL )... great game and first time we beat yis in 9 games ? ( Rugby World Cup )....

Yeah mate, it'd be a real concern, if the floats were made out of concrete! Anyway, good to see Ireland getting up, and don't forget, with a mixture of Hogan and Prendergast blood flowing thru my veins, I have a certain affection for the Emerald Isle! ;D
I was feeling sorry for myself because I couldn't afford new bike boots, until I met a man with no legs.

So I said, "Hey mate, you haven't got any bike boots you don't need, do you?"

 

;
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