See if you can get it to stick in the garage by playing with it while the engine is off and cold. Remember that each time you move the throttle you're squirting a little gas out of the accelerator pump, so you might want to put a little towel under the squirter so you don't have a puddle of gas on the butterflies that leak that then leaks out of the shaft and makes you think you have a gas leak.
You can disconnect your return springs and then manually, with your hand, move the linkage coming out of the foot box to see if you can spot the sticking point. What you really want to watch for is a piece of the linkage coming loose, or getting out of whack, that will cause a lockup regardless of how well it's lubricated. It's probably just sticky goo somewhere along the mechanical connections between the throttle pedal under your foot and the linkage on the side of the carb, but you've got to find it and fix it. This is not a problem to put off until another day.
