Engine on riding lawn mower surging

my thought is the valves are out of adjustment. that is the popping you hear or backfiring. i think if you take off and clean the carburetor and set the valve lash it will probably run like a new one.

This may sound screwy and you all think I'm probably a bit crazy but I have a Troy-Bilt 5550 generator model 01919 and it runs but surges. I also have a Troy-Bilt riding lawn mower which was doing the same thing, when I investigated it, it turned out that my gas tank on my lawn mower had those little "pincher bugs" that I got in my gas tank and was clogging the fuel outlet inside the tank I'm going to check my generator as soon as it cools down this evening as right now it's over 90° outside here in East Tennessee, and see if this is the same issue. Just thought I'd throw that out there it might be crazy talk but can't hurt to check I guess?

If the engine surges take a look at the governor spring. It sounds like the engine is reacting to load

The loud pop is of course, gas vapor exploding inside the heated engine. To alleviate this, let you tractor engine idle for about 15 seconds after mowing before you turn it off.

Pour vinigar and hot pepper sparkles into the gas tank and mix it with the gas. Then start it- the differance in the way it runs will be very noticable!

What kind of lawn trackor do you have and is it a hydromatic?

There is still either water or debree contaminating the fuel system. Surging is usually debree, empty and flush the tank with gas or Iso alcohol, disassemble carb soak in solvent for 30 minutes blow out the carb passages, reassemble and if the problem persists run engine at top rpm with air cleaner off and block off carb intake with hand, this will stall the motor restart and repeat 4 - 5 times this wiil draw out any debree or other blockage in the carb.

sounds like the spring on the carburator butterfly valve is weak ... when at idel it surges the engine but when the blade is enguaged the engine evens out

Depends on how it cuts off. If it gradually slows down over a few minutes or surges, it's likely the carburetor needs to be cleaned and rebuilt. But if it's an immediate cut off, it's likely to be a safety switch such as the one that shuts down the engine when you get off the seat if the mower is running. Sometimes this happens frequently to a light person who bounces on the seat when mowing.