Gas tank getting pressurized - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 8 (permalink) Old 03-31-2017, 08:59 PM Thread Starter
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Gas tank getting pressurized

I am very much inexperienced. I had a bike once before but it was about 20 years ago. I recently purchased a Vulcan. I discovered that it has issues after it has been running a while. Suddenly the RPMs climb significantly. Gas starts spraying out of fuel lines. Then it stalls.
It turns out that the fuel tank is building up significant pressure. Isn't a vent hose supposed to prevent that? If I open the tank after it has been running a little while gas will spray out.
Someone told me that it sounds like the return line may be clogged so my question is, does that sound like a reasonable assessment? If so, does anyone know of a video of some sorts that will point me in the right direction of how to handle it? I can probably just dig in and find it but would feel better about doing it if I had some guidance first.

Thanks!
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post #2 of 8 (permalink) Old 03-31-2017, 09:42 PM
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There's no return line, but it does sound like a vent is clogged.

There's one hose at the rear of the tank (remove seat), unless it's a Calif. model which has a charcoal canister and more hoses. There's also a vent connection where the gas cap closes.

Search for "POOGS" on the site. It's a different condition with the same problem, a clogged vent. There's also posts on the gas cap and vent fixes.

Be careful, could end up with gas in the oil if the pressure can overcome the float valves.
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post #3 of 8 (permalink) Old 04-01-2017, 08:36 AM
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+1 to all above.

would like to add/make more clear. there is NO way for the tank to pressurize other than from heat, due to sunshine or engine heat rising. and of course, the vent valve (in gas cap) or vent line/hose is plugged

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post #4 of 8 (permalink) Old 04-01-2017, 07:35 PM Thread Starter
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I found the hose coming out of tank by the seat. I can freely blow air through it and hear it coming out at the gas tank cap. Air flows through there freely even when the tank has a great deal of pressure in it. I will have to investigate the cap...
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post #5 of 8 (permalink) Old 04-01-2017, 10:08 PM
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I only recall one thread about ripping the cap apart, might be some older ones though. The cap was plugged up in that thread too. There some sort of red plastic plug that the poster maybe drilled or left out, not sure.

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post #6 of 8 (permalink) Old 04-02-2017, 08:13 AM
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the vent valve in the cap can pretty much be gutted. Mine is.

Also, at least for me here in SW florida, during the summer, my gas tank is always whistling.. just the sun heating it up that much.

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post #7 of 8 (permalink) Old 04-02-2017, 10:34 AM
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Quote:
Originally Posted by Spockster View Post
I only recall one thread about ripping the cap apart, might be some older ones though. The cap was plugged up in that thread too. There some sort of red plastic plug that the poster maybe drilled or left out, not sure.
The red plastic plug will not cause the tank to pressurize since the silicone valve is installed to allow air to enter, but not exit the gas tank (i.e., the valve faces into the gas tank). To check the pressure relief, follow the channel in the gas cap from the red plastic plug to a second silicone valve which is installed to allow pressure to exit the tank (i.e., the valve faces out of the gas tank). Below is the POOGS post to clean the gas tank vent system.

https://www.vn750.com/forum/22-carbs-...revention.html


Chris Glennon - Portland, OR
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post #8 of 8 (permalink) Old 04-02-2017, 12:14 PM Thread Starter
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I might not be able to do that til next weekend or so but I will try going through that step by step. Thank you!
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