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amal float level fixture

Classic Norton Commando Motorcycles.

amal float level fixture

Postby seattle##gs » Wed Apr 05, 2017 7:44 pm

I made a fixture for checking amal float levels, it works well but I would like to use water instead of fuel. Is there any difference between the two for finding float levels? Float is float but there might be some goofy difference such as how the viton needle seats and I get a false reading. I really want to get away from using gas.

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Re: amal float level fixture

Postby Torontonian » Wed Apr 05, 2017 8:07 pm

I'm no expert but I Know water sinks and settles below gas so yes there would be a difference.
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Re: amal float level fixture

Postby Deets55 » Wed Apr 05, 2017 9:21 pm

Maybe fill one cup with water and one cup with gas and drop a float in each. If they react the same you should be good to go. I don't think the viton needle tip will be affected by the water or give a different reading than gas.
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Re: amal float level fixture

Postby WZ507 » Wed Apr 05, 2017 10:19 pm

Is it the smell or flammability of gasoline that causes you to seek other test fluids?

Because the density of the test fluid affects the resulting fluid level for a given float setting, you would ideally like your float test fluid to be the same density as gasoline, which typically falls in the range of 0.71-0.74 g/cc. Unless you use another flammable hydrocarbon it is challenging to obtain this density range. Methyl-, ethyl- and isopropyl alcohol all have density around 0.79, so would all be close. Maybe the best solution is to purchase a bottle of 200 proof alcohol (pure ethyl alcohol), which although known to be a toxic human poison, shouldn’t scare you too bad. When you’re done with the float experiment you can make some fruit punch with it and celebrate your successful experiment. :lol:
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Re: amal float level fixture

Postby seattle##gs » Wed Apr 05, 2017 11:04 pm

The smell of gas is overpowering and I have to run the test perhaps 4 times to get the level right...then onto the 2nd carb. by the end of a one or two hour stretch I am really sick of the smell. And I don't enjoy getting fuel on my hands, either. Also, once I adjust the level I would like to run the test 2 more times to make sure it stays the same. That's inhaling way too much gasoline. If isopropyl alcohol is close I can use that. Also, is there any chemical that would remove the fuel residue on the needle? Acetone or lacquer thinner doesn't seem to do it. I realize buying new ones is the way to gobut often the needles and jet ARE new, they've just been sitting unused in the carbs for a year.

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Re: amal float level fixture

Postby gtiller » Thu Apr 06, 2017 12:16 am

I would suggest that with the volumes we are dealing with inside a floatbowl versus the size of the float, the difference between petrol and water would be absolutely negligible.
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Re: amal float level fixture

Postby WZ507 » Thu Apr 06, 2017 4:50 am

gtiller wrote:I would suggest that with the volumes we are dealing with inside a floatbowl versus the size of the float, the difference between petrol and water would be absolutely negligible.

Sounds like a simple enough question to get a quantitative answer to since seattle##gs has made the test rig and can easily test gas, alcohol and water at a fixed float setting. The only comment I’d add is that carb bodies are typically contaminated with sufficient residue that water does not wet well on them (water can bead up and does not wet like gasoline on oily and contaminated surfaces), thus a drop of surfactant (dish soap) in the water is necessary to lower the surface tension of the water so it readily wets the gas line and carb components. Before running the experiment be sure to put a drop of water in the carb bowl to assure it wets, otherwise you are introducing another issue that you don’t want present in your experiment.
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Re: amal float level fixture

Postby acadian » Thu Apr 06, 2017 5:32 am

water is denser than fuel, given equal volume, the water will have more mass, I believe this will have the effect of giving a higher float level position for water vs fuel (same volume)

edit: quick calculation - at similar volumes water is approx. 25% denser than fuel, so to get the actual difference in float height, you'd need to figure out the actual weight and volume of the float itself, then multiply that by the density of the fluid. This is based on the buoyancy principle that any body completely or partially submerged in a fluid (gas or water) at rest is acted upon by an upward force the magnitude of which is equal to the weight of the fluid displaced by the body
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Re: amal float level fixture

Postby Deets55 » Thu Apr 06, 2017 5:34 am

Not to prevent you from doing your experiment, but I would like to share what I have already tried. I built a test rig with the proper 10 degree tilt and used gasoline as the test liquid. I also made a test hose that screws into the float bowl to test the fuel level while on the bike. But the simplest thing I tried, and compared it to the test stand and hose was a small piece of angle aluminum. First I marked the inside of the float bowl (forward end) at 1mm down. Then I installed the needle, float, and float pin. I used the aluminum angle to trap the float pin so there was no movement. I had to cut a notch out of the aluminum to allow the float arm to move freely. Then I just flipped the bowl over and compared the top of the float to the 1mm mark. Adjusted the float till I was happy with the result and then tested it on the stand, and on the bike. The results were the same on all three tests. So now I just use the aluminum angle to adjust the float and final check it on the bike. Be careful of a couple of things if you are using Stay-Up floats. When you bend the tang it is possible to reduce the float pin opening and pinch the pin in the float and also make sure the float tang isn't twisted after you bend it
Hope you find this helpful.

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Re: amal float level fixture

Postby david7212 » Thu Apr 06, 2017 7:27 am

Deets55 wrote:Not to prevent you from doing your experiment, but I would like to share what I have already tried. I built a test rig with the proper 10 degree tilt and used gasoline as the test liquid. I also made a test hose that screws into the float bowl to test the fuel level while on the bike. But the simplest thing I tried, and compared it to the test stand and hose was a small piece of angle aluminum. First I marked the inside of the float bowl (forward end) at 1mm down. Then I installed the needle, float, and float pin. I used the aluminum angle to trap the float pin so there was no movement. I had to cut a notch out of the aluminum to allow the float arm to move freely. Then I just flipped the bowl over and compared the top of the float to the 1mm mark. Adjusted the float till I was happy with the result and then tested it on the stand, and on the bike. The results were the same on all three tests. So now I just use the aluminum angle to adjust the float and final check it on the bike. Be careful of a couple of things if you are using Stay-Up floats. When you bend the tang it is possible to reduce the float pin opening and pinch the pin in the float and also make sure the float tang isn't twisted after you bend it
Hope you find this helpful.

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any pics of this test bench?

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Re: amal float level fixture

Postby Yakatak » Thu Apr 06, 2017 8:30 am

As a chemical engineer,(retired, but the physics haven't changed :) ) I can tell you that the liquid used WILL make a significant difference in float level. I'd use isopropyl alcohol...very similar specific gravities. Miscible with petrol, so will "wet" properly.
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Re: amal float level fixture

Postby Deets55 » Thu Apr 06, 2017 8:56 am

david7212 wrote:
Deets55 wrote:Not to prevent you from doing your experiment, but I would like to share what I have already tried. I built a test rig with the proper 10 degree tilt and used gasoline as the test liquid. I also made a test hose that screws into the float bowl to test the fuel level while on the bike. But the simplest thing I tried, and compared it to the test stand and hose was a small piece of angle aluminum. First I marked the inside of the float bowl (forward end) at 1mm down. Then I installed the needle, float, and float pin. I used the aluminum angle to trap the float pin so there was no movement. I had to cut a notch out of the aluminum to allow the float arm to move freely. Then I just flipped the bowl over and compared the top of the float to the 1mm mark. Adjusted the float till I was happy with the result and then tested it on the stand, and on the bike. The results were the same on all three tests. So now I just use the aluminum angle to adjust the float and final check it on the bike. Be careful of a couple of things if you are using Stay-Up floats. When you bend the tang it is possible to reduce the float pin opening and pinch the pin in the float and also make sure the float tang isn't twisted after you bend it
Hope you find this helpful.

Pete

any pics of this test bench?

I suspended a quart bottle that gear lube came in. Cut a hole in the bottom and connected some fuel line to the cap. Poured some fuel in the quart bottle and let it fill the carb bowl in normal fashion.
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Re: amal float level fixture

Postby Nater_Potater » Thu Apr 06, 2017 9:09 am

As pointed out by a few posters, water, having a higher density, will cause the float to rise much sooner (~25% sooner) than petrol. Water has a density of 1 gram per milliliter, versus 0.71 to 0.77 g/ml for petrol. In other words, the float will close off the needle/seat much sooner than petrol would. If you were to adjust the tang (assuming you could bend it that far) using water, then the petrol would never have the chance to shut off the fuel, leading to an extremely over-full condition. For a great visual, throw the float into a glass of water, then repeat in petrol. The float will bob up like a cork in water, but sit much lower in petrol. The same would happen in the float chamber of the carb.
As for the smell and skin irritation, prop up a fan behind you, and wear thin rubber (surgical) gloves. Even rubbing alcohol gets annoying after a short period of time, and rinses away all the oils from your skin quite nicely. Nothing really gained over petrol.

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Re: amal float level fixture

Postby seattle##gs » Thu Apr 06, 2017 9:29 am

Using a small fan seems the best way. I did not take into account a 10 degree tilt..is it still 10 degrees with a rider?
I have found that it really pays to set the float level first before doing any other carb work.

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Re: amal float level fixture

Postby Triton Thrasher » Thu Apr 06, 2017 11:49 am

There's more to working out a difference in buoyancy than just the density of the medium.
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