Outdoor Power Equipment and Small Engines - Push mower needs to be tilted back to keep engine running

I have a 3.5hp Tecumseh push mower that just had a new carb kit installed. The mower will start, but as soon as I start going down hill, it wants to die out. The only way to stop it before it stalls is to tilt the mower up. I'm guessing the carb is getting flooded. Also, once it stops or I intentionally stop the mower, it is very hard to restart. Usually I can only get it going by taking the air filter out, which by the way was just cleaned.

How long ago was the oil changed? Its amazing the way new oil can completely change the way a mower runs.

This may sound like a stupid question but...How much fuel is in the gas tank? If it is half or better, i'd check to see if the float level was inadvertantly set too low whereas the fuel bowl isn't filling with enough gas to operate at angles. Check too, that the fuel line isn't pinched or kinked.

Actually, I just changed the oil. The other weird thing is after the mower has been run for awhile, it doesn't seem to have this problem. So maybe i does have something to do with the float height and the amount of fuel in the tank after running for ~15 minutes.