Confusing float height

ECP89

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Sorry for another float height thread... But I cant find the answer.

Im setting up my 1980 Bs34's... Cleaned a few times, new pilot plugs, new float valve+seat. All thats left is setting float height.

So the carbs are sitting upside down, bowls off. The Haynes says 32+-1mm. Ive also read ~26mm. Which one is correct for my carbs? Remember it has the plastic floats.

More importantly; what is the correct way to measure the height?
-carbs right side up (floats on bottom), float valve open. Measure from gasket surface to lowest point of float.

-carbs upside down. Floats sitting with no force besides gravity.

-carbs upside down. Floats lifted up until they start opening the valve.


?
 
26mm is for the brass floats; I can tell you that much.

Carbs upside down.
Let the floats sit; don't lift them up or touch them at all.
Measure both sides of each float; they can easily get bent.
Ruler goes on the gasket surface seating area; not the lip.
If the gasket is in place and you're measuring over it you need to add its height; usually 1 or 2 mm.

The photo shows how to measure, but don't take the height shown as an answer. In the photo the ruler is measuring over the gasket, so the actual height is about 32mm, not the 30mm shown on the ruler.
 

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with plastic floats its 2mm fuel line below the top of the float bowl join.

Its a lot easier if you take the carbs off and clamp it level in a vice as you may have to undo the bowl a few times to adjust the floats.
 
I would think the correct, and consistent way, would be to measure right side up, with fuel in the bowls. Seems to me both float types would need to keep the fuel level at 2mm below float bowl seam. That way you don't have to worry what float design you have.
 
I think the Haynes manual is mistaken setting the plastic floats to 32mm. You would have to bend the tang at an incredible angle to attain 32mm. I set my plastic floats at 22.5mm. Here is the resulting fuel level, I'm happy with that.

Nice post; an actual photo backing up that float height is perfect. I agree that 32mm, at least on my brass floats, was just crazy because the floats literally had no travel; they would always be closing the needle.

I would think the correct, and consistent way, would be to measure right side up, with fuel in the bowls. Seems to me both float types would need to keep the fuel level at 2mm below float bowl seam. That way you don't have to worry what float design you have.

This is correct; even after setting mine to the known 26mm for brass floats I took the time to check the level with a clear tube. It is also fairly common to have two slightly different float heights (+/- 1mm or so) if you're measuring it this way.
 
OP, do not be sorry. This forum is here for us to learn and share the passion. You posted at the right time as I am getting ready to work on mine.

There are some experts in here that will lead you in the right direction.
 
thank goodness for this post i was wondering what the measurement was for the fuel method cuase i think its alot better because floats can be bent in wierd ways and what not..
 
also when measureing with fuel in bowls what the refernce level is it 2mm where the bowls sit against the carbs ??
 
Yes, 2mm below the carb body. Not the gasket or float bowl which is about 1mm lower. And don't forget to account for the surface tension (remember grade school science class?) of the gasoline in the tube, which will make the level appear slightly higher in the tube.
 
26mm is for the brass floats; I can tell you that much.

Carbs upside down.
Let the floats sit; don't lift them up or touch them at all.
Measure both sides of each float; they can easily get bent.
Ruler goes on the gasket surface seating area; not the lip.
If the gasket is in place and you're measuring over it you need to add its height; usually 1 or 2 mm.

The photo shows how to measure, but don't take the height shown as an answer. In the photo the ruler is measuring over the gasket, so the actual height is about 32mm, not the 30mm shown on the ruler.

BC, the Yamaha service manual actually says to lift the floats and then "lower [them] until the float arm just touches but does not depress the tip of the float needle." Is that in-correct?

I am actually thinking about switching my carbs to plastic floats since they are actually available and are $4 cheaper/pc. Drewpy and Specdog, did you guys measure your float heights just touching or fully depressing the float needle? And before I go ahead and order the plastic ones, I can replace the brass with plastic, correct?:confused:
 
This how I measure mine a couple of days ago
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So the carbs are sitting upside down, bowls off. Ive also read ~26mm. Which one is correct for my carbs? with the brass floats floats.

I compensated for gasket thickness which is 1mm.Its home made made out of gasket material.Si went with 26.5mm.I hope it works I should they were quite a bit off before.
 
how bout in inches anyone??? the book says... xs250 and 360 = 1.046 +or- .040... but xs400= 1.260 +or- .040 ..... i have calipers... i'm sure i could convert but i don't have anything in metric to measure.

i said screw it i'm tired of it running bad yesterday.. i took the carbs out thoroughly cleaned them and tried to set my floats as the book says but i'm thinking it should be at 1.046 not 1.260 bc it was closer to one originally ... also changed the plugs..
now it runs horrible and obviously its the floats by the way it runs (or doesn't run lol)...
i also still have a timing issue and i have to get that timing cover off there, convinced there's some crap inside!
 
how bout in inches anyone??? the book says... xs250 and 360 = 1.046 +or- .040... but xs400= 1.260 +or- .040 ..... i have calipers... i'm sure i could convert but i don't have anything in metric to measure.

i said screw it i'm tired of it running bad yesterday.. i took the carbs out thoroughly cleaned them and tried to set my floats as the book says but i'm thinking it should be at 1.046 not 1.260 bc it was closer to one originally ... also changed the plugs..
now it runs horrible and obviously its the floats by the way it runs (or doesn't run lol)...
i also still have a timing issue and i have to get that timing cover off there, convinced there's some crap inside!

Just multiply the mm's by .03934 to get the inch measurement.

Still waiting to hear if I can replace brass floats with plastic and the new float height measurement.:confused:
 
I would go with the brass ones. They don't take up as much room in the bowl and seem to be easier to adjust. But that is just my 2 cents.
 
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