Expert: Wayne S. - 10/2/2007

Question
My question...how is a gas tank vented and how do I unplug it?  I own a 1982 Suzuki 1100 L model.  I repainted it 4 years ago and lined the tank with epoxy to prevent rust.  Since then if I fill the tank too full, as the gas expands it comes out through the gas cap.  It has done it enough to mess up the paint.

Answer
Marty,

-the older bikes vent through the gas cap.
When the air in the tank expands the fuel and the air
pressure escape together through the cap or cap vent.

-Check your gasket, replace the cap or
get another vent installed and seal off
the cap vent: http://www.thinkauto.com/onewayvalves.htm

-Thats about the only solutions, the vent
needs to be near the top of the tank.

-NOTE: the tank needs to be able
to get air in and out so the fuel
doesn't get vacuum locked (no fuel flow)

-Later bikes have tank vents with hoses that
run into an emissions can to burn the vapors.

-Under the gas cap assembly you might have a
small hole on the left side.
If so this is attached to a tube that
goes through the fuel tank and exits the bottom
on the right side.
From there it goes through a rubber line to the
bottom of the bike. This is an overflow
and may be plugged up.