Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums - View Single Post - Bike reeks of gas after running
View Single Post
post #8 of (permalink) Old 04-19-2018, 10:56 AM
Senior Member
cglennon's Avatar
Join Date: May 2008
Location: Portland, OR
Posts: 731
iTrader: (0)
Send a message via Skype™ to cglennon
Originally Posted by TonyO View Post

It was quiet in the garage today and I was running in and out a lot fixing an intercom issue . Noticed a hissing noise that i thought was the water softener next to the bike, on closer inspection it was coming from the gas cap. When you get real close the hissing has some bubbling too. Bike was toasty after an hour running in 90 degree weather and gas tank was very warm and more than half full. So I found the source of my gas smell as there is gas around the cap.

Found a bunch of threads related to POOGS fixes discussing issues with the gas cap vent valves getting dirty/stuck/old and stiff (does that sound like someone we know?) so it looks like a gas cap dismantle is in my future.
Hissing from a hot gas tank is normal and means that the pressure relief portion of your gas cap vent is working properly. The hissing is the release of excess air pressure caused by expending fuel (heated by the sun, engine, or fresh gas from a cold underground storage tank). So, this does not sound like POOGS.

POOGS is a situation where the gas cap vent cannot breath (intake) due to blockage. This usually results in a vacuum created as the fuel level drops in the tank and no air can enter the tank to displace the falling fuel level. That vacuum prevents the gravity feed of fuel to the carburetors at approximately 1/2 tank, engines starve for fuel, stall. Open gas cap, relieve vacuum, close gas cap, repeat.

I would still clean the gas cap as a preventative measure. However, it may not solve your problem as the small amount of vapor escaping from the tank should not cause enough gas smell that can reach throughout your house, unless the bike never cools down and the fuel continues to be heated and vaporized (e.g., parked in the sun). There is a small silicone valve on the exhaust port of the gas cap vent that you can verify is still soft and functioning (follow the gas cap vent channel to the very end), but the port it closes off when there is no pressure in the tank is tiny (hence the hissing).

Another option is to park the bike outdoors, in a shaded area, until it cools completely, then move it into the garage. If you still smell gas, then you have a problem other than POOGS (after verifying the silicone gas cap valve is intact). Also, send your wife out to walk around the garage. Women generally have a greater sense of smell than men. She might be able to pinpoint the source.

Chris Glennon - Portland, OR
cglennon is offline  
For the best viewing experience please update your browser to Google Chrome