Topic: CB550K1 Float Height Setting

[franklynb]

Well, thanks to this forum, I'm closer to having this leaky needle problem sorted out on this
CB500K1.

I replaced all the needles, and made a gauge to set the float height at 24mm, when measured
from the bowl mounting surface.



The needles still leak, but I'm perhaps 2 or 3mm from "ideal". "Ideal" would be where
the bottom of the float touches the wire of the gage.

The problem is that the float tabs are at a very weird angle of presentation to the needle spring:


The "tab" that is furled around the pivot boss on the float frame isn's squaring up to the line of
travel of the needle. I'd expect this to cause sticking, either on open, or close, as the tab tries
to bend the needle against the wall of the needle jet.

Can anyone verify that this is "normal"? I'm thinking that perhaps someone previously "unfurled"
all the tabs rather than just bending them into position, which makes the presentation angle
unworkable. If I adjust for more float height, the angle will get worse than shown above.

Any "local knowledge"?

--frankb

[Frostyboy]

I woukd have to suggest that those aren't the correct needle &/or seats in there.
The tangs on my floats are almost paralell with the arms on my floats from memory.
I also set mine with the carbs with the float hinges at the top with the floats hanging so that the spring in the needle doesn't compress. The specs say 22mm I thought.
Hope you sort it out. I have some old float valves in the shed somewher I can measure up for you if you want.

[lucky]

Float height for your motorcycle is 22mm or .866 thousandths.
There is something wrong. Did you order the float needle and seat or just the float needle?
Was it metal tip or rubber tip?

I turned the photo on its side to make everyone happy but the new plastic floats are so light that the float does not push the pin down.
But do the measurement while on its side just to make sure.
With the older brass floats it WAS an issue.

[LesterPiglet]

The float height should not be measured with the carbs upside down. They should be measured where the tang just touches the valve.

[franklynb]

FrostyBoy:

The needles and seats are new. Honda OEM. And a dead match, geometry wise, for the old ones.

lucky:

you are correct. Since I wanted to set my float height INSTALLED, in other words a "wet shutoff height"
I added 2 mm of "fudge" room to accomodate unknown spring compression value. Its easier
to shim up the float than make more room if its short. Confused myself with the CB750 dimension.

LesterPiglet:

Perhaps you are correct. But I agree with lucky. The plastic float gravity load on the pins is almost negligible in terms of
setup height, and certainly as good as the pivot straightness on old floats. PLUS. Have you actually TRIED to level four floats in one rack
vertically? I haven't measured, but  I doubt the pivots are anywhere near plumb enough! And if every float requires a separate
"tweak" to get the "barely touching the pin" setup factor -- doesn't that just defeat the POINT of setting the float heights at once?

Anyway, the goal is to be able to tweak the float height to "perfect" closing levels -- on the bike.

And here's the picture -- from the FSM -- that makes me think there was once a bend in the tab.
This was the essential question in my post. Anybody seen a brand new one?

[LesterPiglet]

Perhaps you are correct. But I agree with lucky. The plastic float gravity load on the pins is almost negligible in terms of
setup height, and certainly as good as the pivot straightness on old floats. PLUS. Have you actually TRIED to level four floats in one rack
vertically? I haven't measured, but  I doubt the pivots are anywhere near plumb enough! And if every float requires a separate
"tweak" to get the "barely touching the pin" setup factor -- doesn't that just defeat the POINT of setting the float heights at once?

Yes, it is not difficult and it is the correct procedure. Mine look like that picture and I know they haven't been touched before me.

Sorry, the second picture.

[DH]

Something aint right with those float tangs. You may be onto some
thing about how they're "unfurled". If someone could post a pic of a good float uninstalled, it would help. The pin of the float needle should sit flat on
and perpendicular to the float tang. The tang is like a platform. Lightly bending the tang determines measured float height. Yours most certainly look as if they would bind for sure. The tangs look deformed. The arms that hold the pontoons may have been bent in an attempt to alter float height too, and that's a no no as well.
Looks like a previous owner's unsuccessful attempt to stop floodingout the overflows...just a guess, hopefully someone that really knows
will verify. When you get it right the reward will be worth the trouble.
good luck with it.

[lucky]

Do not add any "wet" height adjustment or "fudge factor" stuff. You are way over thinking this.

I will post a photo of how the float tang should look.

If they are really bent up you may have to get new floats.

[lucky]

Here are photos to help you.
Do you have that steel spring clip that goes on the main jet?
Anyway study these photos.

I wish we could see a photo of one of your float needles.

[franklynb]

lucky!

CB5003 hits "the nail on the head".  The bend curvature of the "ramp" in my tabs is all but
destroyed, flattened into a uniform slope. I'll need to make a little die that reforms the
curve on the mill. Any rough estimate of radius of curvature on that feature? Im guessing 2mm from
the photos ... I'd guess a sharp corner would work, but don't want to create a stress riser in the
old tab.

If you can just provide a depth measurement of the tab surface from the top and bottom of the pivot
"roll" I can figure it out and compare my calculated "tab length" to your actual.

I'll take some macros of the needles later today when at the shop. New floats? $50 each, and the
"while you're in there" stuff has really piled up on this one -- so I'm trying to keep the bill from another
tsunami crest ...

[lucky]

Too bad someone bent those floats all up like that.

[franklynb]

Here's a little more data:

I photo'd and measured the "tab" best possible:



And here's a "money shot" of the needles; old on the left.


Since I now think I have the real problem surrounded, I slightly modified a vice grip,
using in it a vice to create a forming mandrel:



And then clamping the pivot lightly enough to hold it in place, did a little "refurling" by walking
the pivot around and successively clamping the vice grip:



and finally, with a hammer and chisel,  put a new bend at the "suspected" 2mm from end of tab point.





And voila! A lot closer to the "real target". Note, by comparing the before and after that I
was able to recover a lot of the furling around the pivot. The new surface is much closer
-- and squarer -- to the needle actuation plane.



 One point that I find  interesting: the spring now loads fully in the horizontal setup,
from the weight of the plastics floats -- where previously, due to the out of square angle,
 the spring had enough side bending stiffness to hold the float up.

So, now it makes a lot of sense to follow LesterPiglet's
advice, and find a way to "final tune" the shape in the vertical setup!  And lucky's tip:
polish the pits out of the tab surface, giving the spring a nice smooth surface to ride.

Hope this helps someone else.

[TwoTired]

I will just say this.
The float valve spring pins on all the stock float valves I have will NOT support the weight of plastic floats.  The float height adjustment MUST be done with the carbs on their sides.

If your valve spring pins are stronger than what was original, so as to actually support the float weight, I predict that you will have to find a new float height measurement different from book values in order to get the same fuel level in the bowls as with the original spring pins.

Cheers,

[bollingball]

 When everything is correct. You cannot measure the float height with the carbs upside down and have a accurate reading.

Ken

[lucky]

I sure do not like the looks of those float needles.
Are those new ones that you bought?
They just look a little rough.

[lucky]

Here's a little more data:

I photo'd and measured the "tab" best possible:



And here's a "money shot" of the needles; old on the left.


Since I now think I have the real problem surrounded, I slightly modified a vice grip,
using in it a vice to create a forming mandrel:



And then clamping the pivot lightly enough to hold it in place, did a little "refurling" by walking
the pivot around and successively clamping the vice grip:



and finally, with a hammer and chisel,  put a new bend at the "suspected" 2mm from end of tab point.

So, now it makes a lot of sense to follow LesterPiglet's
advice, and find a way to "final tune" the shape in the vertical setup!  And lucky's tip:
polish the pits out of the tab surface, giving the spring a nice smooth surface to ride.

Hope this helps someone else.

That was not me (LUCKY), about the polishing of the surface, but it should be smooth.

[LesterPiglet]

Whoopee, I'm glad your problem seems to be solved.

[franklynb]

Yep, 3 weeks old, on the right.
Perhaps 15 minutes on it under flow <engine running>.
The one on the left? priceless.

 

I sure do not like the looks of those float needles.
Are those new ones that you bought?
They just look a little rough.