Gas guage and/or Gas valve problem - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 6 (permalink) Old 10-18-2013, 06:40 PM Thread Starter
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Gas guage and/or Gas valve problem

Hi, new here today.
I have a 2001 Vulcan 750 with 6000 miles. Everything is nearly perfect except the gas guage seems to indicate more gas than it has. It had gone empty when showing about 1/3 full. But a few days ago ir "ran out" [engine faltered and stalled] after only about 55 miles since last fill up, and with showing 3/4 full on guage. I went to reserve and that lasted only about 6 miles. Gas was still visible directly below fill cap! I pushed it a block, then jerked it with sudden braking to slosh gas into tap, and that worked well enough to restart and drive 2 blocks to gas station. It took only about 1.3 gallons to get it to where I usually stop filling[gas level is upon the center part directly below cap.]

So, is there some way the fuel tap could have risen or otherwise malfunctioned so that it runs out of gas while still holding a gallon or two?

Anyone ever hear of such a condition?

How hard is it to repair/replace the fuel guage signal sender? I am tempted to put 2 quarts of gas in saddlebags and drive until I run out as a test, but don't like idea of carrying gas. If I do, would one quart plastic oil containers be ok to use?
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post #2 of 6 (permalink) Old 10-18-2013, 08:02 PM
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Uh, see the thread on POOGS. Your "running out of gas" might be do to this. On a full tank (don't look at the gauge) you should get around 120 miles before reserve kicks in on a full tank.

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post #3 of 6 (permalink) Old 10-18-2013, 10:05 PM
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Pogs or a vacuum leak on the vacuum line between your front cylinder carb and the petcock. It there isn't good vacuum to the petcock the little vacuum diaphragm in the petcock won't open properly cutting the fuel off.

To help you understand how this works try this. With the bike off and a towel under the petcock to catch dripping gasoline remove a gas line from the petcock. you will get a few drops of gas but after that with the bike not running (producing vacuum) the fuel flow should stop. Now unhook the vacuum line between the petcock (center line of the 3 lines, the two outside lines run gas to your carbs) and the front carb at the carb. Lean in and suck on this short piece of vacuum line. Fuel will start to flow out the previously removed petcock fuel outlet.

It you have a vacuum leak in this line or in the boot between the front carb and the head there may not be enough vacuum to open the vacuum valve in the petcock.

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post #4 of 6 (permalink) Old 10-19-2013, 12:52 AM Thread Starter
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Thanks Knife and Fool! I read the POOGS thread. I had never heard of vaccum being used to open up fuel valve on a tank. My 1948 Indian Scout never had that feature! I don't think my 1972 Kawasaki H2 did either, although when new it did have a fuel starvation problem due to lack of air getting into gas tank. Took the dealer repeated efforts to figure it out. Anyway, I guess if it is a vaccum issue with my Vulcan, it is overcome by the sheer weight of the gas if the tank is full, but as the condition gets worse, it takes more and more gas in the tank to overcome it. Is that right?

So, I guess I'll start taking things apart tomorrow.
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post #5 of 6 (permalink) Old 10-19-2013, 07:36 AM
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I had the POOGS hit last weekend. Gas dripping from the groove in the vacuum part of the petcock spacer. Turns out to be a hole in the petcock vacuum diafram. Kit should arrive today.
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post #6 of 6 (permalink) Old 10-19-2013, 03:33 PM
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VulcaPAFL, First realize that POOGS is still the likely cause of your problems with a vacuum leak to the petcock being the #2 potential.

The vacuum valve in the petcock is suppost to keep fuel from flowing past your floats when the engine is off if your float seals don't work well. It also works as a safety device in an accident to help keep fuel from pouring out of your tank.

Note: The petcock vacuum cover also has a little one way ball valve in it (I suspect to keep carb backfires away from your fuel line) which can become "sticky" with time making the ball valve hard to move and making it harder for vacuum to open the petcock.

If you remove the petcock vacuum diaphragm cover you can blow and suck on the brass vacuum nipple and feel the ball move inside. If you ever rebuild your petcock after disassembly before replacing the little vacuum diaphram blow some carb cleaner in through the brass vacuum nipple to help loosen the ball valve up.

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Last edited by Spencer1; 10-19-2013 at 03:41 PM.
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