I have a Husqrvarna LGT2554 riding mower. It sat over winter and had some issues starting. Basically, it'd start, but then sputter and die out. So I figured the gas had turned. I replaced the air filter and the fuel filter, and completely drained the fuel line and replace it all with fresh fuel with a splash of Stabil added. (I also replaced the battery, just to be safe, because I had a spare handy.) But nothing changed. It still starts, but then dies after 3-5 seconds.

The most common troubleshooting advice I've found online at this point is to clean the carburetor or squirt some gas into it -- but in an LGT2554, the carburetor isn't accessible! Any suggestions?

Hi,
Well not all that easily accessible. Remove the air filter cover and filter and pour a little gas down the passage. The engine will draw it in by itself to see if it will start that way. Service manual is here and see page 20 for above:
http://www.kohlerengines.com/onlinecatalog/pdf/sm_32_690_01.pdf
Peace,
Clarke

Hey, thanks for the manual link!

Unfortunately, I tried that and it didn't work. So I just replaced the spark plugs, and it seems like it started a little more easily, but didn't stay started. Sigh.

Any other suggestions? This is driving me crazy.. .

Hi,
I would say it is a dirty carb if the fuel shutoff solenoid is opening.w plugs, did you gap them to 0.030"? It is common for them to come out of the packaging at about 0.045"
Peace,
Clarke

Yes, I gapped them to 0.03". I'm no spark plug expert, though, so I used a gap gauge (on a tool called the Spark Doctor) that's based on thickness -- you close the gap extra-tight, then wedge the appropriately-thick section of the gauge in to open it back to the right size. So it seemed pretty idiot-proof (I hope).

I could definitely believe this being a carb problem. Do you recommend any way to clean it that doesn't involve taking the engine apart to expose it fully? I'm an amateur at best and I wouldn't trust myself to get it back together properly. Judging from that manual you linked, it looks like I could get to the top of it at least, if I had to.

Hi,
The manual looks fairly decent. All the fasteners will probably be Phillips head screws and bolts with 8 and 10 mm heads. That does not included the fuel shutoff solenoid which I would guess may be 19mm(3/4".) It is the first thing I would check to make sure that the tip moves freely.
Before that I would use a pair of pliers to disconnect the fuel line from the carb to verify a pulse from the pump. After disconnecting crank the engine over. The pump should send out a fairly significant pulse of fuel.
Peace,
Clarke

Hi,
Another link for the carb, just scroll down to Kohler carbs. Try:
Small Engine, Lawn Mower, Snowthrower Troubleshooting, Repairs and Safety (http://outdoorpowerinfo.com/repairs/)
Peace,
Clarke