I was checking my air filter and noticed it's had a yellow stain on the inside (top), and the filter smells line gasoline.  I don't recall this smell the last time I checked the air filter.    Is this normal, if not, what would cause this?

probably if your bike got knocked over? That's what one of the bike shops told me that could happen. Other users might be able to chime in

my whole garage smells like gasoline so i think your okay. 

it could get that smell from some unburned gas in the chamber during valve overlap, or when the bike is shut off gas that was being pushed up into the carb throat drips into the box, or from air fuel mixture that was being rapidly drawn into the chamber on one stroke suddenly has no where to go but back out the carbs when the intake valve closes for the compression stroke, or a million other way.  i havent laid my bike down and the filter smells like gas. im sure everyones does. its not an issue

Much better than smelling like exhaust!
Smelling like gas is the one smell I would expect from that side of the engine 

could be the carbs leaking back into the airbox and then draining out the bottom, making the whole place smell

that happens to me if i forget to turn it from prime to on when i park, the float valves seep a little bit over time

all i smell is gas when im near the bike lol

Your fuel tank is above the air intake. Maybe there is a slight leak from the fuel line or the petcock seal on the tank and a few drips of gas are leaking out.
Does the tank look all rusty inside?
Any signs of rust or leaking on the bottom of the tank?

Then, maybe you overflowed and spilled some gas last time you filled up and it flowed under the tank and into the air filter.

are you leaving it on prime? gas will keep flowing till carbs over flow.

Quote from: Chanse on September 20, 2010, 06:09:34 PM
are you leaving it on prime? gas will keep flowing till carbs over flow.

Not true..if the needle valves are working correctly, the bowls will fill with fuel, the floats will raise, the needles will go into the needle valve seats, the fuel flow stops...in a perfect world   

You are correct though, leaving a bike on prime is not a good practice 

TRUE Actually. Ive had my needles gum up and not function like their supposed to.

Quote from: Chanse on September 21, 2010, 08:01:52 AM
TRUE Actually. Ive had my needles gum up and not function like their supposed to.

Only when the needle valves are shot, in your post you claim..."gas will keep flowing till carbs over flow" is only true if you have bad needle valves, don't make it sound like it "will" for everyone when 90+% of the bikes out there left on prime will have NO problems whatsoever.

also the crankcase breather goes straght into the airbox, and the crankcase, naturally, smells like gas/oil.  youre all really over analyzing this. when you find me a gs whose air filter doesnt smell like gas ill send you 20 bucks.  but you gotta send me the bike.

Pardon'.......   MAY...         and also original post asked "what 'would' cause this"..  As there are many causes. Mine is just One of them..

Quote from: Chanse on September 22, 2010, 03:44:29 PM
Pardon'.......   MAY...         and also original post asked "what 'would' cause this"..  As there are many causes. Mine is just One of them..

Sorry for being so anal...I get that way some times 

i had this problem with my gz250.the main thing you have to watch for is petrol in your oil,it comes back into the crankcase from the filter some how.i took my bike to workshop and the mechanic took a quick look and told me it would be cheaper to replace carb with reco/secondhand.than look for problem in old one.took his advice got a carb and came up trumps.as for what caused it your geusse is as good as mine.