I use one that looks just like this….http://www.walmart.com/ip/Pennzoil-Siphon-Pump/16795103. It uses 1/4 tubing, so it works great. I remove the fuel line running to the carb on top of the fuel tank, and put one end of the siphon on it. The other end goes into my race fuel jug. Pinch the line before you squeeze the bulb, and when you release the bulb release the line, and it should start siphoning. Basically you are using your existing fuel pickup hose inside your tank, so it empties your tank almost completely.
With the kart on a stand I pull the fuel line from the carb while pinching it and let it self-siphon into a gas tank on the shelf on the kart stand… Usually drains to very little left in the tank…I usually don’t dump that, but it’s not hard to pull the tank and dump that residual amount out if needed.
I use this one. It works great, you just shake the hose a few times and the flow starts. I empty my tank in about a minute without pumping manually. You can also get it at lowes, where all the pool and water supplies are.