Small Engines (Lawn Mowers, etc.): Go-cart, alcohol briggs

Question
QUESTION: I have an old go cart that I bought and it will crank but it shortly goes dead. It
has a 5 hp Briggs on it.  It's got an alcohol jet in it. I am running it with
alcohol in it. I have gone thru the carb and replaced pick up tubes, diaphram
and gaskets. It sat up for about 6 years. It's got an air intake on it. It will
crank near about every pull. It just won't continue to run. Longest it has run is
about 1 minute. I keep having to put my hand over the air intake to choke it
and keep it from dying. This works sometimes. I am running out I ideas. It's
got a new spark plug. Gets great fire. Good compression too. It also has a
tuned pipe on it. Please help. How do I keep it running?

ANSWER: This has the carb-on-tank set-up?

Under the carb in the tank, where the small tube sits, there's a small bowl.  Is that filling up with fuel?

---------- FOLLOW-UP ----------

QUESTION: It does have the carb on top of the tank. It's filling up with gas as far as I
know. It's a fairly new tank that I put on it. The original had to much rust to
salvage.

Answer
If the fuel bowl, the small tank within the tank, is filling, then you probably just need to clean the carburetor really good.  The fuel nozzle, the tube in the middle, may be plugged up.  You may even need a new carb.  

Alcohol is hygroscopic, meaning it absorbs water.  And it does it very well.  It also evaporates quickly, which causes deposits to be left behind.  It's also rough on the rubbers used in small engines, so seals, diaphragms, O-rings and gaskets will deteriorate quicker.

I would go through the carb and not be afraid of replacing it.  You have an overly lean condition and that needs to be corrected before you try and operate the engine much.  Running it too lean will result in pre-detonation and overheating and has to be avoided.

Another thing to consider is that an engine requires about twice as much alcohol as straight gasoline.  This will make it harder to tune as you can only get these little carburetors to flow just so much fuel.  Drilling the hole for the nozzle out and using a larger fuel nozzle may be helpful.  I would recommend you find someone with a dyno that specializes in Kart racing if you want to try to get the most performance out of it.