I have an old go kart (10 years) with a 5hp B&S engine. I haven't used it in at least 6 years (when I was a kid). Recently I started it up and drove it around some. It was fine the first two times and didn't even seem to have a problem running the old gas. Recently I tried to use it again and after about 5 minutes I had trouble going up a hill. When I applied power, the engine would start to die and make popping noises resulting in the go-kart surging from engine misses. I continued to drive the kart like this and it got to the point where if I gave it some gas, the engine would just start to cut off and not move the kart at all. When I let off the gas, the engine would stop dying and would idle fine again. But the kart wouldn't move at this point. When I finally killed the engine, it was hard to re-start.

I let the engine sit for a few weeks, put some new gas in it, and tried it again, but it seemed like the same problem started to happen again, this time after only about a minute of driving the kart (faster than before).

What do these symptoms suggest?

Dead clutch?
Bad spark plug?
Fuel filter (remember I was running it with 8 year old gas at first)?
Carb (I sprayed a bunch of carb cleaner down the choke - didn't do anything -- I also removed the air filter and tried to drive with no air filter and it had the same problem so the air filter wasn't cauing the trouble)?
Some more serious engine damage (valves, etc.)?
Something else?

What do I need to do to figure out what I need to fix?

I beat on this engine hard when I was a kid. I rode it like everyday and never changed oil or filters or anything because I didn't know any better. But it ran great until the day I grew up and now after sitting it's not working anymore.

Thanks!

What could be going on is that the pickup tubes in the tank might have some clogged screens. If you remove the carburetor from the gas tank, you will see two long plastic tubes that come out with it depending on how old the engine is. If it was made in the last 20 years or so, then it will likely have these plastic tubes. if not, it might have one. On any count, they have a brass screen covering the intake. if the gas sat in there for a long time, then all kinds of crap and rust might have accumulated and gotten stuck in the screen. You might also have a clogged needle jet. Pull out the screw and see how dirty it is and if it is covered in varnish. If it is, get some Q-tips and clean out the orfice and then clean the needle too.

Agree with briggsrepairman on suggestions, also check the fuel pump diaphragm it's on the side opposite the adjustment screw. There are 4 little screws holding the cover on and when you take it off be careful not to loose the spring and cap that is under the diaphragm. Over a period of time this diaphragm can get hard and brittle or get a hole in it and then it will not pump fuel out of the tank properly.

Good Luck

And if it has foam (sponge like) in the tank.... make sure thats not disintegrating.....

might be a good idea to change the oil, air filter, and spark plug since it sat so long.....just to be safe