I have a 1997 Yamaha 400 Kodiak 4x4 and its the fuel is stopping at the carburator.  I have taken the gas line off of the carburator and there is plenty of gas.  If I take the drain plug out from the bottom of the carburator it just trickels out.  Does anyone know what the problem is?  

It sounds like the carb float might be getting stuck closed, possibly by a build up of gunk in the carb. Try disassembling the float bowl, cleaning the float and needle with carb cleaner, move the float manually(open and close the fuel passage) at the same time you spray the cleaner.
Hope this helps.
-Marty  

Try an easy fix first.  Get some "seafoam" from your local auto parts store.  Run it in, full strength, through your gas line.  You will hear a difference in how the atv runs once all the gas has gone through the carb and it is burning the seafoam.  The atv may die but that's no problem.  Let it sit for about 15-20 minutes.  This will eat away at the "junk" inside the carb.  Restart it and see how it runs.  Most likely it will improve.  I have used this on my atv, a generator that was running poorly etc.  It's a cheap, easy fix.  If that doesn't work, disassembly may be needed.  Good luck, Greg  

if you yank the carb be sure to not move any air/fuel mixture screws.

take the carb off the bike, then take the bowl off the bottom (normally four screws)
you'll have access to the float there,  look inside the bowl for trash, rust, water etc..  if there's water you'll need to dump the tank to get rid of it.
next:
remove the pin that holds the float assy, once you do this the float and needle valve will fall out.  DONT LOSE THEM!!!
inspect the float for holes or cracks.  check to see if the float has fuel inside of it.
it shouldn't have fuel inside it.  if it does it will fill up and weigh down the float never letting it close.
and you'll need to replace it.

once you have finished inspecting the float, remove the top of the carburetor, there will a diaphram inside with a round cylinder, gently pull it out (it should come out easily)
check the needle on the end for wear and the diaphram for holes or perforations.

once you have all of this out of the carb, take a wire bread tie, burn the plastic or paper off the bread tie.  then insert it gently into any small holes you find in the carburetor housing make sure they are all clear.  wipe out the carberetor, inspect to be sure the carb is clean, then replace the float, needle valve and float pin, then replace the diaphram and top end of the carb. reinstall the carb and see if it doesn't fire up for ya.

hope this helps.
ps... when you are through riding turn off the fuel valve on the tank and run the engine until it burns all of the fuel out of the carb.
but don't forget to turn the fuel back on the next time you go out to ride.  

I had a similar problem with my grizzly 600. turned out somehow a piece of rubber got stuck in the valve seat holding it open. i did exactly what wolf has suggested and fixed it in 5 minutes.