Floats, Clear Tube Method

Does anyone have a post or have a detailed description on how to do a Clear Tube Test on the floats?? I've been advised to do one and I cant find details on how to do this procedure. I think my #2 carb is low cause no matter how I tune the Idle Mixture screw it just doesnt want to turn tan, or black even for that matter. So I think once I get me floats dead on I think most my tuning troubles will be over.
-SLkid

 

the whole post is a good read


look at the pictures on this link


http://xjbikes.com/Forums/viewtopic/t=2 ... rt=45.html

 

Ok, so i know the carbs have to be leveled, no big deal, I can make a rig in ten minutes. Gas tank Up high, connected to the carbs fuel port. Do you put it on PRI and fill up all the bowls? Or do you put it on ON and suck on the vac hose till the floats supposedly shut off the flow to all 4 bowls?
Ok, and after you fill the bowls, you connect a how long peice of fuel line to the drain ports. I see in pics that you hold the fuel line below the fuel bowl, is there a certain angle? or will gravity keep the same "Level" in the tube?
First time doing this and I dont ahve a manual. So I'm just trying to get an idea for when I pull my carbs off again so I can do this.
-SLKid

 

Length should not matter, the tube level should be the same level as a the bowl.


I set mine to pri then let it fill the bowls for a few min before testing.

 

If you set it on PRI, how do you know you're float needles are actually shutting the valve off?

 

I have a clear fuel filter on mine so I can see the gas stop.

I have only done this once, had to it do about four times to get it where I wanted it, but I assumed if the floats did not close correctly, the gas would have continued to flow, & flow out of the airbox boot & cylinder openings.

I am sure you could do it with on & the vacuum method but then you have to remember to give it more vacuum to replace the gas that is filling the tube during measurement.

 

Well, even if your floats close properly, in the PRI position the gas will still flow, overfilling the bowls and leaking into your airbox boots.
I hear of Fitz using Washer Fluid to fill his bowls, easier clean up and not as smelly I assume. I like the idea of using washer fluid, but how what are some other ways to fill you bowls and get a proper accurate reading, maybe using an alternate tank source so I dont have to put washer fluid in my gas tank
-SLkid

 

Well i was reading a little bit and I guess that if your floats are working properly, sitting at Level, they wont let gas flow even in the PRI position. Sorry Kendal. I was wrong. So I guess thats what I'll do. And when the gas stops, I'll attach a clear tube and drain one fuel bowl at a time, angling the clear tube while its draining and see where it stops related to the top of the Fuel Bowl. Correct?

 

I filled them all up then measured fuel level in each, once that was done I turned off or removed the fuel source.

Then after I had the measurements, I drained all 4 bowls, one at a time back into a gas can. made my adjustments & repeated the whole thing if they were still off.

Once i got one perfect in my opinion I dry measured it & then made the others match before I filled them again.

I did do a bench sync with 2 paperclips that I saw in the faq section, at that point they were close enough to give it a test start, Fired up after 2 cranks.

 

Ok, I think i got it now. And when I make adjustments, bending the tang towards the carb body (Edit)HEIGHTENS the fuel level, while bending it away (Edit)LOWERS the fuel level.
Cool, I think I got enough Info to do this now.
Thanks Kendall!
Any other opinions welcome! Always can use more information
-SLKid

 

Bending the float away from the carb body lowers the float level. Bending the float toward the carb body raises the float level.


this was a quote when i asked the same thing in a different thread they have some nice pics too

http://xjbikes.com/Forums/viewtopic/t=1 ... rt=30.html

 

Actually, if fuel is overflowing from the bowls, one or more of your needles is not closing properly. That's the whole purpose of those valves, to stop fuel flow into the bowls once they have enough in them.

Incidentally, I don't recommend washer fluid as a testing fluid. (Sorry, Fitz!) I tried it recently, and it seemed to work fine at first. I set the levels perfectly, drained the washer fluid, then cleaned the leftover fluid out of the bowls (or I thought I did, at any rate). I put the carbs back on the bike, put the tank on "prime" to refill the bowls, and walked over to the bench to get the key. By the time I got back to the bike, there was gas EVERYWHERE. :evil:

Took the bowls back off, and there were blue crystalline deposits all over the inside of the bowls, on the needles, and inside the seats (they were spotless before I started, btw). Somehow some fluid remaining in the bowls must have reacted with the gas, and man, was it a pain to clean out.

To top it off, when I went to recheck the levels with gas, they were significantly lower than they had been with the washer fluid (about 2 mm), which tells me that the fluid must be more buoyant than gasoline, which means you can't get a good reading with it anyway.

Just my experience, YMMV...

 

Ummm........not quite right, and of course when you say "bending the float" you are really referring to the bending of the "tang arm" of the float which contacts the needle.

If you bend that tang "down", away from the carb body, then the floats must rise that much further and "higher' in order to shut off the fuel flow (by pressing the needle upwards into its seat).

So bending the tang "down" will increase the amount of fuel that enters the bowl before the fuel flow is cut off, and thus RAISE the fuel level in the bowl.

Remember, it's the proper fuel level that you're shooting for; a certain float height is just an associated aspect of the whole procedure...


Trying to set the fuel level by some arbitrary value of the float "height" is the road to frustration, imo. The replacement needle/seat units may or may not have the same dimensional characteristics as the original units supplied by the manufacturer. And in most cases, the "measuring points" that would be used to determine a "float height" are unknown------yes, one measuring point is known (the carb bowl body, where the gasket sits, but without the gasket in place), but the other measuring point is, at best, vague, or in other case, unknown. Even for the few carbs where the factory manual has an illustration of what they consider the "float height", or when they describe that upper measuring point ("the top of the float"), it's still vague, unclear, subject to individual interpretation.

A better way would be to:

* make sure you are using the same float needle valve assemblies in all four carbs.

* set any one carb up properly (the proper fuel level, set in the proper manner, i.e. carbs level, etc.),

* now, measure and determine the "float height" of that one, known, valid properly set carb, using any two reference points as your "measuring points". The base flange of the carb body to "X".....and you can make "X" anything that you want, at any point on the float that you want, and as long as you do the other 3 carbs in the exact same manner, they also should be set properly.

* of course, check your results on all carbs when done.

 

Well stated Chacal.

When you replace your float needles, unless they have the exact same dimensions as the originals (not likely... even if only wear and age is considered), you will have to make adjustments.

Also... if you are concerned with precision... only the grade of gasoline that you will be running with will provide an accurate basis for measuring float height. What you need is a fluid that has the SAME specific gravity as the gasoline that will end up being used. That being said, I know of no fluid that is an adequate equivalent of gasoline.

And remember, temperature of the gas also effects its specific gravity, although to lesser extent, but suffice to say that gasoline that has been sitting out in the sun for 8 hours and is 90 degrees has a markedly lower specific gravity than gas that is 50 degrees. Whether you can adjust the floats to that precision is doubtful.

 

When I cleaned my carbs, I used windshield washer fluid to check the float heights before taking them apart. WW fluid was a good choice for downstairs next to the water heater and furnace. To set the floats after rebuilding, I used gas and went out to the shed.

 

Wow! Thats a lot of good info! Thanks guys!
When I got my new aftermarket needle seats the differance in the OEM seats to the aftermarkets was about 5mm of float level height. So it took a lot of adjusting to get to the factory setting of 17.5mm. So, Chacal is right once again
-SLKid

 

Soooo windshield fluid - not a good idea?
So many people backed it, that's what I used.
Should I retest with gas?

 

Only if you would stoop so low and be so foolish as to pay any credence to the official service manuals, which should all be re-named "Fantasia: The Big Bogus Book of Bovine Excerement That We Foist On You, The Gullible, Wide-Eyed, Believing Public (and onto our own people, too)", since their procedure specifically calls for using windshield washer GAS, not just windshield washer "fluid".......

 

Uh, WHAT. lol.

Is that a sarcastic hint to get me to use GAS only, OR is there really such thing as windshield washer GAS. lol.

 

Sure, it goes in the reservoir right next to the blinker fluid! :lol:

 

See there! HE read the manual........

 

O_O

^--- That's what I look like right now. Reading that.

Sarcastic punks. lol.

 

In all seriousness, dpawl, if your plugs tell you that the mixture is fine and you're not having fuel supply issues, you might be OK. I'd personally pull the bowls and check, after seeing what I had to clean out of mine (I really should have taken a picture).

Note that I'm not trying to say that the washer fluid method hasn't worked for some people; I just wanted to point out for other folks here that I tried it, and it caused me more problems than it solved.

 

So what's the attraction to WW fluid as opposed to straight up water? Is it the color? Is it the alcohol or the antifreeze additives? Are you guys thinking that it has enough alcohol in it to bind the residual water to the gas when you're done? Are you thinking that it has a specific gravity closer to gas?

I understand the concept of doing a float level ballpark "reality check" using something safer and less smelly than gasoline, but why not just use water with a little food coloring in it? If you're worried about residual water in the system, then maybe run a little drygas through with your first tank of gas? Maybe today's ethanol blends have enough already?

Sorry if this has all been hashed through already...

So what do you think the temperature of the gas is in a black tank on a hot day sitting in the sun over top of a hot engine?

You suggesting we need a "float bowl level measurement temperature standard?"

 

WW fluid has a SIMILAR specific gravity to that of gasoline and therefor, in theory, will allow the floats to "float" at the same level in either fluid.

Think back to 8th grade science (i know, it's been a while, but try to keep up). When the teacher put the egg in fresh water, it sank. but when the egg was placed in salt water, it would float. This is because the salt in the water changed the specific gravity of the fluid.

Water (distilled) at 64° F, has a specific gravity of 1.000, whereas gasoline at the same temperature has a specific gravity of around .755-ish.

At 90° F, the specific gravity reading of standard gasoline is .747. However, at 60° F, the number is .760.

I would argue that this slight of a difference (.013) is not enough to cause much concern. However, the difference between water (1.000) and gasoline (.755) is MUCH greater (.245) and should cause much different readings on your carb floats.

I do not have the specific gravity of the WW fluid but i expect it would be similar to gasoline. When i get some free time, i'll test WW fluid S.G. against gasoline S.G.

 

I understand specific gravity, but WW fluid is mostly water with some alcohol (usually either isopropyl or methyl) added and sometimes they add some propylene glycol as well for additional low temp freeze resistance.

Quickly obtained unverified web-surfing-obtained numbers:
Gasoline - 737
Isopropyl - 785
Methanol - 791
Propylene Glycol - 965

If memory serves the VOC content in WW fluid is something like 30%. and at that concentration, the SG shouldn't be that much different than straight water. And water doesn't (shouldn't) have any other additives, like salts, that could cause a problem inside the carbs. Use distilled if you're worried about it?

I guess the point is... I know that water isn't what you want in your carbs either, but at least you know what it is!! Is the slight reduction in SG of WW fluid really worth it? :?:

 

i see your point, and it is a good one. if those numbers are correct, then you certainly wouldn't want to use WW fluid. But i certainly wouldn't use water either. I would stick to gasoline unless you find another liquid with the same SG.

 

Yeah, obviously gasoline is the benchmark stuff to use but I do see the benefit of the less volatile reality check before the final gasoline test. I mean, if you use water and your bowl level is low, you can be sure that it will be even lower with gasoline, right? Haven't rolled the concepts around in my head enough to be confident in the numbers, but if it's ratiometric, it should be like 25% lower with gas? :?:

I'm currently in the middle of some carb work and float measurement will certainly be part of the process. I'm not there yet, but I'm trying to get my ducks in a row ahead of time. Thanks for the help!

 

lower, yes, but i don't know if the equation is linear enough to say 25%. I, for one, would just use the gasoline, red one carb level, drain, set the float accordingly, and measure it to set the rest. Then just one final check with gasoline again. i wouldn't want any water in my carbs anyway. Just my opinion.

 

Well this is getting awfully interesting...

Did a little search, got ahold of this.
http://www.cjmillerllc.com/msds/Msdsonl ... 000288.pdf

Windshield washer fluid w/ ~35% methanol.
Specific gravity = 0.95

That's way closer to water than gas... Now I need to redo my floats again...

This research should be recompiled in a clean format (all the posts above) and then STICKIED.
Probably better off buying a bottle of rubbing alcohol. That would do the trick right? Because that is isopropal, and going by your statement above, it is "Isopropyl - 785" which is damn close to gas.

 

Yeah that is real close to gas. Not less smelly, but wouldnt be wasting your hard earned dollars for that gasolina.
-SLKid

 

ahh yes, good old MSDS. rubbing alcohol would be closer to gas, but do you know what's even closer?... I bet you can all guess where i'm going with this. lol.

 

Did some calcs in my head and came up with a need for 24% less volume of float submerged for water than gas to float the same body (float rides higher in water than gas. There for if you use water or fluid it will be off conciderably.

For warm gas versus cold gas, the calc comes to 1% more volume for hot gas than cold gas.

So temp doesn't matter, but fluid density should.

But let me ask this. (I may have the carb backwards in my head).

If waterish thing is used the float is higher for a given level of "fuel". (We want the fuel to get to a certain hight in the bowl and then stop comming in). Since the float is up you would have to bend the tang away from the carb (delaying the trigger of the valve closing) to get the "fuel" up to the correct level. Now you put in gas. The float sits conciderably lower in the gas (effectively further delaying the cut off) and you should have an overfull situation?

I guess I'll just use gas in a well ventilated area away from ignition sources.

 

I keep telling ya'll to use tequilla to set the floats ... this way everything is set right and nothing goes to waste if you cleaned it thoroughly.

"I guess I'll just use gas in a well ventilated area away from ignition sources." - i have this very same policy

 

It may burn like gasoline, but the density isn't close...

 

within 30kg/cu.m at 50deg ...... i guess you havent heard the term "eyeball it" or "good enought for government work"

 

i forgot to mention after releasing the tequilla you need to re-test to verify that the individuals density is not greater that that of the tequilla

 

Lol, ya'll are a trip. I enjoy the technical disscussion in this thread too

 

So it might be more accurate for the float levels, but hold on... don't alcohols do bad things to assemblies that aren't designed for it? I know there are a lot of classic car guys who will never put standard pump gas in their tank for that reason, and that's just a 90/10 gas/alcohol mix (which is pretty much all you can get here in corn country...). Anybody know what pure alcohol will do to your seals/passages?

Something else I just thought of: I'm assuming that the SG number you're quoting is for pure Isopropyl Alcohol... which isn't typically available to the public. The bottle I have in the medicine cabinet is 70% alcohol, so you've got 30% by volume of water throwing off the calculations again. My brother uses the 97% pure stuff in a medical research lab, and he said that it's far more volatile than gasoline, so if anything, that would be less safe than just using gas in the first place.

 

They sell 90% at the drug store as well.
But you do make a valid point, 10% will still be water.

As far as it damaging anything, I do believe it's more of a running motor problem, I don't think it hurts anything. Hell, those top fuel drags and stuff run alcohol right?
Then again they rebuild their motors, like, twice a day lol.

Just stick with gas.

Save the rubbing alcohol for some fun with the firepit out back O_O
(douse the logs then light em... oh yeah)

 

"Top fuel" motors run nitro-methane, a rocket propellant and industrial explosive. When you see those video imagines on TV where they're blowing up the sides of mountains to do strip-mining? That's nitromethane.

The main production plants for it in the US were in a small town named Nitro, West Virginia.

Alcohol classes run alcohol.

They rebuild the engines (or substitute freshly rebuilt ones) after each pass. A big part of the job is to read the bearings after each run, to determine whether fuel mixtures, supercharge boost pressures are properly set. If they don't squish the main and rod beaings flat, then they know that something's wrong.......

BUT, don't try this at home! Top fuel engines are designed to live their entire lives turning over a mere 900 total engine revolutions before they are rebuilt or relegated to the scrap heap....

 

Yeah I meant the alcohol class, wasn't sure which ones run it really. I just knew some ran alcohol.

I should have bought some nitromethane off my uncle from the drag strip and tried in it my Yamaha Chappy... HAHA. WEEEE.

BTW - my worst 'accident' ever... was doing 21MPH on a dirt trail, on a YAMAHA CHAPPY MOPED. Yep. Details anyone?

 

Haha, man I love this discussion! You guys have learned some physics (not to mention creative writing techniques from Chacal!) while you are rebuilding your XJ.... gotta love this website.

That being said I will throw one more element of uncertainty into the mix... due to age, each float will sit a slightly different level in the carb, thus the reason for setting each one separately.

If all floats are new, and are within tight tolerances in terms of weight and dimensions you could set one bowl with gas then set the rest to that dimension and be pretty dead on.

One final note: Didn't mean to make such a big deal about the temperature effect on the specific gravity of gasoline..... It doesn't make much difference in setting floats, but in the aviation industry we have to factor the temperature into the specific gravity reading. We are about to load 8000 gallons of AVGAS into our storage tanks and once its pumped in there... if aint right... we bought it.

 

ahh yes H.G. Wells taught us about the fourth dimension "Time" and its affect on the universe. so my proposal is to manufacturer an injection mold fuel safe clear plastic replacement for the carb bowls. tell me that wouldnt be accurate and really cool at the very least.

 

not just that but you could see any debris or poor fuel delivery readily prior to any real damage. ...


ohhh this gives me several new ideas

 

Another safe working fluid that won't readily burn or explode in your lap, ??
Diesel !!
What's the SG difference to gas ? I'd bet it's close, and you could throw some alcohol in it to get it exactly right.

 

diesel fuel is anywhere from 0.810 to 0.960. too far from the 0.740-ish of gasoline IMO. alcohol (rubbing alcohol) has a higher SG than the gasoline to begin with so it can't dilute the diesel down to the correct SG.

 

Really, that high? Then gasoline and safe working conditions it is.
Hey, how about cooking oil?

 

somewhere around 0.915-ish

 

Wow, talk about gum city...