Gas Fumes - Page 2 - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
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post #11 of 14 (permalink) Old 06-02-2019, 12:29 PM
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I don't see a problem, if it's whistling, it's working. The nipple is in the tank itself.

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post #12 of 14 (permalink) Old 06-02-2019, 03:51 PM
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The nipple should be part #92093, and it appears it is no longer available. Now I'm glad I have a CA tank. I can use the evap overflow fitting for a vent, and plug up the hole where the nipple goes if it melts. When I bought my '93 new, I had all kinds of starting and running issues with it. The dealer told me to only fill the tank 3/4 full, because if you tried to fill it all the way up, liquid gas would run into the charcoal cannister, then get sucked into the intake, causing it to run too rich. 3/4 FULL! He had to be kidding. I immediately ripped out the entire evap system so I could fill my tank all the way up.

The whistling indicates a difference in pressure between inside the tank and outside the tank. It should be the same. It should have an unobstructed vent to the atmosphere. I saw a Yamaha V-Star 650 that the tank was crushed on. Some part of the evap system had failed, and allowed a vacuum to build up in the tank, and the tank collapsed.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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post #13 of 14 (permalink) Old 06-02-2019, 04:11 PM
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I may have been wrong about the nipple, but the vent opening is built into the tank under the cap, if I recall.. Quite a few have reported the whistle, but none have had POOGS that I recall.

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post #14 of 14 (permalink) Old 06-03-2019, 04:08 PM
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Originally Posted by VN750Rider/Jerry View Post
The whistling noise is coming from a valve in the gas cap. Take the cap apart and remove the valve, and the whistling will stop. The noise is cause by the valve releasing pressure in the tank. If the tank is properly vented, there should never be any pressure in it. It's part of the emissions control crap. I purged my bike of every tiny little bit of that stuff. My 1997 still has all that crap on it. It is going to be fun removing it. I should box it up and ship it to the EPA.
This valve in the cap is what properly vents the tank. That valve prevents gas from leaving the tank whenever it sloshes around. It's not an EPA additive, but a "keep the gas in the tank" additive.

I hate the EPA as much as the next fellow, but this valve should stay in place.


'89 Vulcan 750 Bought 4/12/18 @ 17805.9 miles $800
Purchased stock. Wrecked once
26980.4+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB
110/90 Front Tire
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages
Ear Shave (wo/ coasters) 40/140 NO shims 45MPG
MCCT conversion

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