Float level advice, please.

[Captain Obvious]

Arrgh... Stupid floats!! These things are working me over! I'm finding it difficult to get the fuel level high enough.

Is it conceivable to think that maybe today's gasoline has a higher specific gravity than the gas they were using forty years ago? Heavier gas makes the floats more buoyant and that drops the fuel level? Maybe some sort of EPA thing to slow down evaporation?

Or am I just losing my touch? 

[Patcon]

Denser gas might have less evaporation therefore more desirable from an EPA  perspective. Maybe the gas is less pure, uses a heavier portion of the barrel???

[siteunseen]

I accidentally set mine a little higher than my 23mm mark. That was 6 years ago and they've been great.

Context...

Rude marking using my phone. Red is 23mm scratch, yellow is where the valve closes.

 

 

[Mark Maras]

A while back I looked through older SU (including Hitachi) books and forums about the float level heights. 
Many of the sites said the same thing. "The float levels aren't critical but the fuel level should be near 3/8" below the carb bridge". That would place the fuel level 9.525 nozzle turns down from the top.

[Captain Obvious]

Well maybe it's extra floaty aftermarket floats or something. I'll post a pic of what I got going on when I get a chance.

The problem I'm having is that the level is too low. So I bend the tab down some. Level comes up some, but not enough. And then when I keep bending the tab down, I eventually run into the situation where the float mechanically bumps into something (underside of the lid or inside of the bowl chamber) before the valve closes, and it overflows.

Basically, I can't bend the tab down far enough to bring the level up to spec before I run out of compliance. It's like the float is too floaty.

I got tired of messing with it before and went ahead and bough all new parts... New aftermarket valves. New aftermarket floats. I was hoping it would all magically come together with the new parts, but no joy.

I've got some antique OEM (not aftermarket) floats here... Maybe I'll see how they float.

[AK260]

I’m certain you would have considered this but is there any way of adding mass to them? For example a small self tapping screw at the very top? Or if not enough, making the hole slightly larger and adding lead shot, then sealing up with a bung, screw or silicone sealant?

[Captain Obvious]

Yup. Absolutely considered it. That and/or taking material off the bottom of a floaty float.

But I guess my first order of business was to try to find out  if it's just me.      If it's just me, maybe I need to go back to float school.

I think today I'm going to try to measure the density of an old OEM float alongside a new aftermarket version. I've already weighed them (and they're the same to the resolution of my scale), but I haven't measured their volumes.

[Mark Maras]

Have you determined if the float is bumping the float chamber wall or the lid?

[AK260]

Yup. Absolutely considered it. That and/or taking material off the bottom of a floaty float.
But I guess my first order of business was to try to find out  if it's just me.      If it's just me, maybe I need to go back to float school.
I think today I'm going to try to measure the density of an old OEM float alongside a new aftermarket version. I've already weighed them (and they're the same to the resolution of my scale), but I haven't measured their volumes.

In that case we shall follow your floaters with interest! :p

[Captain Obvious]

I bought fresh gas (just in case the two week old stuff had started to evaporate, thereby driving up the specific gravity) and then I took some pics of the situation.

Here's my basic quick thrown together test rig. The carb lid is sitting on top of a small glass. The masking tape is just to provide a little stability to the lid so it doesn't slip off the glass:

Here's and aftermarket float right out of the package. Tab looks like this:

And here's what the fuel level looks like with that float. This is for the front 72 (long ear) carb, so the target is 22 mm down from the bottom of the lid. I'm way low:

So I bend the float tab to adjust the level. And after a couple tries, it looks like this:

The level is close, but still a little low. Big problem, however, is that I've run out of compliance. You can see in this pic that the float is so tilted that it's hitting the underside of the lid. A put a little extra pressure on the fuel inlet and it pushed past the valve and kept going:

The other problem with the float being this tilted is that you can actually end up on the downhill slops side of the valve tang.

So I also tried an old OEM used float and got similar results. About that only thing I can come up with is the gas is higher gravity than it was forty years ago.  Fresh premium grade from the local station?

Surely it can't be just me. Can it? I've done countless floats in the past. Am I just losing my mojo? 

Edited June 9, 2021 by Captain Obvious
typo

[Patcon]

Is the needle valve too short?

[Captain Obvious]

Nope. 72 Long valve. Right on spec.

And the rear set-up does about the same thing. For the pics, I just grabbed the long ear lid 50/50 chance.

On edit - But that's a really good question. Because what started this whole thing in the beginning was a mixmash of incorrect parts including a short valve on the long ear lid. I was hoping that with all new parts in the right positions, all the problems would magically go away.

Edited June 9, 2021 by Captain Obvious